Santaji Gadepatil

Founder & Editor, Zenta Calculator

Santaji Gadepatil is the founder of Zenta Calculator. He works in industrial instrumentation and digital marketing, with hands-on experience in flow, level, pressure and temperature measurement. He checks the formulas, units and worked examples of every calculator before it is published.

LinkedIn profile

Areas of expertise

Industrial instrumentation
Flow, level, pressure and temperature measurement
Process automation
Digital marketing and SEO

Calculators by Santaji (444)

4–20 mA Loop Resistance Calculator (Maximum Loop Load)Check whether a 4–20 mA loop has enough voltage — maximum loop resistance from supply and transmitter lift-off voltage, with cable and barrier resistance.
4–20 mA Scaling CalculatorConvert a 4–20 mA loop current to a process value (and back) for any measuring range — with live scaling chart.
555 Timer Calculator (Astable Mode)Calculate the frequency, duty cycle, high time and low time of a 555 timer in astable mode from R1, R2 and C — or choose parts for a target frequency.
Acceleration CalculatorCalculate acceleration from change in speed and time — or the final speed or time needed — in m/s², g and more.
Acres to Hectares ConverterConvert acres to hectares and hectares to acres — plus square metres and square feet.
ADC Resolution Calculator (LSB and Step Size)Calculate ADC step size (LSB), number of levels and the digital code for an input voltage from bit depth and reference voltage — including 4–20 mA PLC inputs.
Add Days to a Date CalculatorAdd or subtract days from a date to find the resulting date and day of the week. Free online add days to a date calculator with formula and examples.
Age CalculatorCalculate exact age in years, months and days from a date of birth — or age on any date.
Alcohol Units CalculatorCalculate UK alcohol units and US standard drinks in any drink from its volume and ABV.
Amps to Watts Calculator (and Watts to Amps)Convert amps to watts for DC, single-phase and three-phase circuits — with charts for 12 V, 120 V and 230 V.
Annuity Payout CalculatorFind the monthly income a lump sum can pay for a fixed number of years — or the lump sum needed for a target monthly payout.
API Gravity Calculator (API to Specific Gravity)Convert API gravity to specific gravity and density and back — for crude oil, fuels and petroleum products at 60 °F.
Aquarium Volume CalculatorCalculate fish tank volume in litres and gallons from its dimensions — plus the approximate weight when filled.
Arc Length & Sector Area CalculatorCalculate arc length, sector area and chord length of a circle from radius and central angle.
Area ConverterConvert square metres, square feet, acres, hectares, square yards and more — type in any field. Free online area converter with formula and examples.
Arrhenius Equation CalculatorCalculate the reaction rate constant from activation energy, temperature and pre-exponential factor.
Aspect Ratio CalculatorResize images and video while keeping the aspect ratio — find the missing width or height.
Availability Calculator (MTBF and MTTR)Calculate equipment availability from MTBF and MTTR, plus failure rate, expected downtime per year and the probability of running without failure.
Average Calculator (Mean, Median, Range)Paste a list of numbers to get the mean, median, minimum, maximum, range, sum and count instantly. Free online average calculator with formula and examples.
Bacterial Growth CalculatorPredict bacterial population after a given time from the starting count and generation (doubling) time.
Baker's Percentage Calculator (Dough Hydration)Calculate dough ingredients from flour weight and baker's percentages — water (hydration), salt, yeast and more.
Baseball Batting Average & OBP CalculatorCalculate batting average, on-base percentage (OBP) and more from hits, at-bats and walks.
Basketball Shooting Calculator (FG%, eFG%, TS%)Calculate field goal percentage, effective field goal percentage and true shooting percentage.
Battery Charging Time CalculatorCalculate how long a battery takes to charge from its capacity, charging current, starting charge level and charging efficiency — lead-acid or lithium.
Battery Life CalculatorEstimate how long a battery will last from its capacity (mAh) and the device's current draw. Free online battery life calculator with formula and examples.
Beer–Lambert Law Calculator (Absorbance)Calculate absorbance, concentration or molar absorptivity using A = εlc, plus transmittance. Free online Beer–Lambert law calculator with formula and examples.
Bike vs Car Commute Savings CalculatorCalculate the money, CO₂ and calories saved by cycling instead of driving to work. Free online bike vs car commute Savings calculator with formula and examples.
Binomial Probability CalculatorCalculate the probability of exactly k successes in n independent trials with success probability p.
BMI CalculatorCalculate Body Mass Index from weight and height in kg, lb, cm or inches — or find the weight for a target BMI.
BMR & Daily Calorie CalculatorEstimate your Basal Metabolic Rate (BMR) and daily calorie needs (TDEE) with the Mifflin–St Jeor equation.
Board Feet Calculator (Lumber)Calculate board feet of lumber from thickness, width and length — plus total cost.
Body Fat Calculator (US Navy Method)Estimate your body fat percentage from waist, neck, hip and height measurements using the US Navy formula.
Body Surface Area Calculator (BSA)Calculate body surface area (BSA) from height and weight using the Mosteller formula.
Boiling Point Elevation CalculatorCalculate how much a dissolved solute raises the boiling point of a solvent using ΔTb = i·Kb·m — for water, ethanol, benzene and more.
Boost Converter Calculator (Inductor and Capacitor)Calculate duty cycle, input current, inductor value and output capacitor for a boost (step-up) DC-DC converter.
Box Volume Calculator (Rectangular Prism)Calculate the volume, surface area and diagonal of a box or rectangular prism — in litres, cubic metres, cubic feet or gallons.
Boyle's Law Calculator (P₁V₁ = P₂V₂)Calculate new pressure or volume of a gas at constant temperature using Boyle's law.
Break-Even CalculatorFind the break-even point in units and revenue from fixed costs, selling price and variable cost per unit.
Brick CalculatorEstimate the number of bricks for a wall from its size, brick dimensions and mortar joint — with waste.
Brine Calculator (Salt Percentage)Calculate how much salt (and sugar) to add for a brine of any strength — for meat, pickles and fermentation.
Buck Converter Calculator (Inductor and Capacitor)Calculate duty cycle, inductor value, ripple current and output capacitor for a buck (step-down) DC-DC converter.
Buffer pH Calculator (Henderson–Hasselbalch)Calculate buffer pH from pKa and the concentrations of weak acid and conjugate base — or the ratio needed for a target pH.
Buoyancy Calculator (Archimedes' Principle)Calculate the buoyant force on an object in water or another fluid, its apparent weight and whether it will float — using Archimedes' principle.
Butter Converter (Sticks, Grams, Cups, Tbsp)Convert butter between US sticks, grams, cups, tablespoons and ounces.
Cable Voltage Drop CalculatorCalculate voltage drop in copper or aluminium cable for single-phase and three-phase circuits — and the minimum cable size.
CAGR CalculatorCalculate the compound annual growth rate (CAGR) between two values — or project a future value from a growth rate.
Cake Pan Size ConverterScale a recipe for a different round or square cake tin by comparing pan areas. Free online cake pan size converter with formula and examples.
Calorie Deficit & Weight Loss Time CalculatorEstimate how long it takes to lose weight at a given daily calorie deficit — based on about 7,700 kcal per kg of body fat.
Calories Burned Calculator (MET)Estimate calories burned during walking, running, cycling, swimming and other activities from body weight and duration.
Calories from Macros CalculatorCalculate total calories from grams of protein, carbohydrate, fat and alcohol — as shown on nutrition labels.
Capacitor Energy and Charge CalculatorCalculate the energy stored in a capacitor and its charge from capacitance and voltage — for supercapacitors, DC links and flash circuits.
Capacitors in Series and Parallel CalculatorCalculate the total capacitance of up to four capacitors in series or parallel, with the total voltage rating guide and charge.
Car Carbon Footprint CalculatorEstimate CO₂ emissions from driving based on distance, fuel consumption and fuel type. Free online car carbon footprint calculator with formula and examples.
Carbon Offset Cost CalculatorCalculate the cost of offsetting your emissions at a given carbon price per tonne. Free online carbon offset cost calculator with formula and examples.
Cat Age Calculator (Cat Years to Human Years)Convert your cat's age into human years using the widely used veterinary guideline. Free online cat age calculator with formula and examples.
Cell Doubling Time CalculatorCalculate population doubling time and growth rate from starting and final cell counts over a time interval.
Cent to Sq Ft ConverterConvert cents to square feet, square metres and acres — the land unit used in Kerala, Tamil Nadu, Karnataka and Andhra Pradesh.
Centrifuge RPM ↔ RCF (g-force) CalculatorConvert centrifuge speed between RPM and relative centrifugal force (× g) using the rotor radius.
Centripetal Force CalculatorCalculate centripetal force and acceleration for an object moving in a circle from mass, speed and radius.
CGPA to Percentage CalculatorConvert CGPA to percentage using CBSE, AICTE, Mumbai University and other common formulas — or convert percentage back to CGPA.
Charles's Law Calculator (V₁/T₁ = V₂/T₂)Calculate new volume or temperature of a gas at constant pressure using Charles's law.
Circle CalculatorEnter a circle's radius, diameter, circumference or area and get the other three instantly, in any unit.
CM to Inches ConverterConvert centimetres to inches and inches to centimetres instantly, with a handy conversion table. Free online CM to inches converter with formula and examples.
Coefficient of Variation CalculatorCalculate the coefficient of variation (relative standard deviation) of a data set to compare variability.
Coffee Ratio Calculator (Coffee to Water)Find the right amount of coffee and water for any brew ratio — pour-over, French press, drip or cold brew.
Combination Calculator (nCr)Calculate the number of combinations — ways to choose r items from n when order doesn't matter. Lottery odds included.
Combined Gas Law CalculatorSolve P₁V₁/T₁ = P₂V₂/T₂ for any unknown — pressure, volume or temperature of a fixed amount of gas.
Commission CalculatorCalculate sales commission and total pay from sales, commission rate and base salary — or the sales needed to reach an earnings target.
Commute Time Calculator (Hours per Year)See how many hours and days per year you spend commuting — and what that time is worth. Free online commute time calculator with formula and examples.
Compost C:N Ratio CalculatorCalculate the carbon-to-nitrogen ratio of a mix of two compost materials — greens and browns.
Compound Interest CalculatorFind maturity amount, interest earned, rate or time for any compounding frequency — with a growth chart and step-by-step working.
Concrete Column & Footing Calculator (Round)Calculate concrete volume for round columns, piers, post holes and sonotubes. Free online concrete column & footing calculator with formula and examples.
Concrete Mix Calculator (Cement, Sand, Aggregate)Calculate cement bags, sand and coarse aggregate for nominal concrete mixes like M15, M20 and M25.
Concrete Slab CalculatorCalculate the concrete volume for a slab, patio or driveway — plus pre-mix bags needed, with a waste allowance.
Cone Calculator (Volume, Slant Height, Surface Area)Calculate a cone's volume, slant height and surface area from its radius and height.
Confidence Interval Calculator (Mean)Calculate a confidence interval for a mean from the sample mean, standard deviation and sample size.
Control Valve Kv / Cv CalculatorSize control valves for liquids — calculate Kv, Cv, flow or pressure drop from any three values.
Cooking Measurement Converter (Cups, Tbsp, ml)Convert kitchen volume measurements — cups, tablespoons, teaspoons, fluid ounces and millilitres.
Cost Per Use CalculatorWork out the true cost per use of a purchase — clothing, gadgets, gym memberships and more.
Coulomb's Law Calculator (Electric Force)Calculate the electrostatic force between two point charges, or the distance or charge needed for a given force, using Coulomb's law.
CPM, CPC, CTR and CPA CalculatorCalculate CPM, CPC, CTR, conversion rate and cost per acquisition from ad spend, impressions, clicks and conversions — all in one place.
Creatinine Clearance Calculator (Cockcroft–Gault)Estimate creatinine clearance (kidney function) from age, weight, sex and serum creatinine with the Cockcroft–Gault equation.
Credit Card Payoff CalculatorFind how long it takes to pay off a credit card balance with fixed monthly payments — and the total interest you will pay.
Cricket Batting Average & Strike Rate CalculatorCalculate a batter's average, strike rate and boundary percentage from runs, dismissals and balls faced.
Cricket Bowling Economy, Average & Strike RateCalculate a bowler's economy rate, bowling average and strike rate from runs, wickets and balls bowled.
Cricket Run Rate CalculatorCalculate a cricket team's run rate (runs per over) from runs scored and overs or balls faced.
CT Burden Calculator (VA)Calculate current transformer (CT) burden in VA from secondary current, lead length, cable size and relay or meter burden — and check it against the CT rating.
Current Divider CalculatorCalculate how a total current splits between two parallel resistors using the current divider rule — with branch currents and equivalent resistance.
Customer Lifetime Value Calculator (CLV and LTV:CAC)Calculate customer lifetime value from order value, purchase frequency, margin and retention — and compare it with acquisition cost (LTV:CAC).
Cycling Gear & Speed CalculatorCalculate bike speed from cadence, chainring, cog and wheel size — plus gear ratio and development.
Cylinder Volume CalculatorFind the volume and surface area of a cylinder from radius and height — in litres, gallons, m³ or ft³.
Daily Habit Cost CalculatorSee how much a daily habit — coffee, snacks, cigarettes, subscriptions — costs per month, year and decade.
Dalton's Law Calculator (Partial Pressure)Calculate the partial pressure of a gas in a mixture from mole fraction and total pressure — for air, diving gases and gas mixtures.
Data Storage Converter (KB, MB, GB, TB)Convert data sizes between bytes, KB, MB, GB, TB and binary units (KiB, MiB, GiB). Free online data storage converter with formula and examples.
Days Between Dates CalculatorCount the days, weeks, months and working days between two dates. Free online days between dates calculator with formula and examples.
Days Until Calculator (Countdown)Count down the days, weeks and working days until any date — a birthday, holiday, exam or event.
dBm to Watts Converter (and Watts to dBm)Convert dBm to watts, milliwatts and dBW and back — with voltage across 50 Ω — for RF, Wi-Fi, radio and fibre power levels.
Debt-to-Income Ratio Calculator (DTI and FOIR)Calculate your debt-to-income ratio (DTI or FOIR) from monthly debts and income — and see how lenders judge it for home and personal loans.
Decibel Calculator (dB Power and Voltage Ratios)Convert power and voltage ratios to decibels and back — dB gain and loss for audio, RF and signal chains, plus sound levels.
Density Calculator (ρ = m/V)Calculate density from mass and volume — or mass or volume from density — in kg/m³, g/cm³ and lb/ft³.
Dilution Calculator (C₁V₁ = C₂V₂)Calculate how much stock solution and solvent you need to make a diluted solution — or the final concentration.
Discount CalculatorFind the sale price and how much you save from a percentage discount — or work out the discount from the sale price.
Dividend Yield CalculatorCalculate dividend yield from annual dividend and share price — and the yearly income from your investment.
DNA / RNA Concentration Calculator (A260)Calculate nucleic acid concentration from A260 absorbance for dsDNA, ssDNA and RNA, including dilution and purity ratio.
DNA Copy Number CalculatorCalculate the number of DNA molecules (copies) from mass in ng and length in base pairs — for qPCR standards and cloning.
Dog Age Calculator (Dog Years to Human Years)Convert your dog's age to human years using the modern DNA-based formula — and compare with the old "×7" rule.
Dog Food Calorie CalculatorEstimate your dog's daily calorie needs from body weight and life stage — plus cups of food per day.
Doppler Effect Calculator (Sound)Calculate the frequency heard from a moving sound source or by a moving observer using the Doppler effect formula — sirens, trains and more.
Download Time CalculatorEstimate how long a file takes to download or upload at a given internet speed (Mbps). Free online download time calculator with formula and examples.
DP Flow Square Root CalculatorConvert differential pressure to flow for orifice, venturi and other DP flow meters using square-root extraction.
DP Level Transmitter Range Calculator (Wet Leg and Dry Leg)Calculate LRV and URV for a differential pressure level transmitter on open, dry-leg or wet-leg tanks — with zero elevation and suppression.
Drywall / Plasterboard CalculatorEstimate the number of drywall (plasterboard) sheets for walls and ceilings, with waste.
Earth Conductor Size Calculator (Adiabatic Equation)Calculate the minimum protective earth conductor size from fault current and disconnection time with the adiabatic equation S = I√t / k (IEC 60364-5-54).
Earth Fault Loop Impedance Calculator (Zs)Calculate prospective earth fault current from loop impedance Zs, or the maximum Zs for an MCB to trip within 0.4 s — for TN systems.
Earthing Resistance Calculator (Earth Rod)Calculate the earth resistance of a vertical earth rod or pipe electrode from soil resistivity, length and diameter — and how many rods you need.
eGFR Calculator (CKD-EPI 2021)Estimate glomerular filtration rate (eGFR) from serum creatinine, age and sex using the race-free CKD-EPI 2021 equation, with CKD stages.
Electricity CO₂ Emissions CalculatorCalculate the carbon emissions from your electricity use with your grid's emission factor.
Electricity Cost Calculator (Appliance Running Cost)Calculate how much an appliance costs to run per day, month and year from its wattage, hours of use and electricity rate.
Electrolytic Capacitor Life Calculator (10 °C Rule)Estimate the expected life of an aluminium electrolytic capacitor at your operating temperature from its rated hours and temperature, using the 10-degree rule.
Ellipse Calculator (Area, Perimeter, Eccentricity)Calculate the area, perimeter (Ramanujan approximation), eccentricity and foci distance of an ellipse from its two semi-axes.
EMI Calculator (Home, Car and Personal Loan)Calculate your loan EMI, total interest and total payment for home, car, personal or education loans — in rupees, with a chart.
Empirical Rule Calculator (68–95–99.7)Find the ranges containing 68%, 95% and 99.7% of values in a normal distribution from the mean and standard deviation.
Energy Converter (kWh, J, kcal, BTU)Convert energy between joules, kilojoules, kWh, Wh, calories, kilocalories, BTU and therms.
EPF Calculator (Provident Fund Maturity)Estimate your EPF balance at retirement from basic salary, age, yearly salary increase and the current 8.25% EPF interest rate.
ERA Calculator (Earned Run Average)Calculate a baseball pitcher's earned run average (ERA) and WHIP from innings pitched.
Escape Velocity CalculatorCalculate the escape velocity from any planet, moon or star from its mass and radius — with values for the Earth, Moon, Mars and more.
EV Charging Time CalculatorWork out how long it takes to charge an electric car from your current level to a target — at home, on a wallbox or at a fast charger.
EV vs Petrol Car Running Cost CalculatorCompare the energy cost per km and per year of an electric car against a petrol or diesel car.
Excavation & Dirt CalculatorCalculate excavation volume in m³ and cubic yards, including soil swell, and the number of truckloads needed.
Exponent Calculator (Powers & Roots)Calculate x to the power n, find the nth root, or solve for the exponent — type in any two fields.
Exponential Population Growth CalculatorCalculate future population with continuous exponential growth from an initial size, growth rate and time.
Factorial Calculator (n!)Calculate the factorial of a number (n!) exactly up to 170, with the number of digits and a table of factorials.
Fahrenheit to Celsius Converter (°F to °C)Convert Fahrenheit to Celsius and Celsius to Fahrenheit instantly — with charts for weather, body temperature, cooking and ovens.
FD Calculator (Fixed Deposit)Calculate fixed deposit maturity amount and interest with quarterly, monthly or yearly compounding — for SBI, HDFC, post office and other bank FDs.
Feet to Inches ConverterConvert feet to inches and inches to feet instantly — including feet-and-inches heights and lumber lengths.
Feet to Meters ConverterConvert feet to metres and metres to feet — including heights in feet and inches. Free online feet to meters converter with formula and examples.
Fence Calculator (Posts & Panels)Calculate the number of fence posts, panels or rails and the concrete needed for any fence length.
Final Exam Grade CalculatorFind the score you need on your final exam to reach a target course grade. Free online final exam grade calculator with formula and examples.
Flight Carbon Emissions CalculatorEstimate CO₂ emissions per passenger for a flight from distance, cabin class and non-CO₂ effects.
Flooring Calculator (Laminate & Wood)Calculate how many boxes of laminate, vinyl or wood flooring you need — with waste and total cost.
Flow Meter K-Factor CalculatorConvert pulse frequency to flow rate (and back) for turbine, positive displacement and other pulse-output flow meters.
Flow Rate ConverterConvert volumetric flow between m³/h, L/min, L/s, US gpm, CFM and m³/s — for pumps, pipes and flow meters.
Food Cost & Menu Price CalculatorCalculate cost per serving and the menu price needed to hit a target food cost percentage.
Force Calculator (F = ma)Calculate force, mass or acceleration using Newton's second law, F = m × a, in newtons, kN or lbf.
Fraction to Decimal ConverterConvert any fraction to a decimal and percentage — or a decimal back to a fraction value — instantly.
Free Fall CalculatorCalculate fall time, impact speed and fall height for an object dropped from rest, ignoring air resistance.
Freezing Point Depression CalculatorCalculate how much a solute lowers the freezing point of a solvent with ΔTf = i·Kf·m — for water, benzene, cyclohexane and more.
Fuel Cost Calculator (Trip Cost)Calculate the fuel needed and the cost of a trip from distance, fuel consumption and fuel price — and split it between passengers.
Fuel Economy Converter (L/100 km ↔ mpg)Convert fuel consumption between L/100 km, km/L, US mpg and UK mpg. Free online fuel economy converter with formula and examples.
Future Value CalculatorCalculate the future value of a lump sum plus regular monthly deposits, with compound interest — or find the deposit needed for a goal.
Gaj to Sq Ft Converter (Square Yards)Convert gaj (square yards) to square feet, square metres and other land units — the plot measure used across North India.
Gallons to Liters ConverterConvert US and UK gallons to litres instantly, with charts for fuel, water tanks and cooking. Free online gallons to liters converter with formula and examples.
Garden Watering CalculatorCalculate how much water a lawn or garden needs per week and how long to run a sprinkler or hose.
Gas Flow Correction Calculator (Actual to Normal m³/h)Convert actual gas flow (Am³/h) to normal or standard flow (Nm³/h, Sm³/h) using line pressure and temperature — for flow meters and compressors.
GC Content CalculatorCalculate the GC content (percentage of guanine and cytosine) of a DNA or RNA sequence from base counts.
GCF and LCM Calculator (HCF and LCM)Find the greatest common factor (GCF/HCF) and least common multiple (LCM) of two numbers, with the Euclidean method explained.
Generator Size Calculator (DG Set kVA)Calculate the diesel generator (DG set) kVA rating needed for your connected load, power factor, future margin and largest motor start.
Geometric Mean CalculatorCalculate the geometric mean of positive numbers — the correct average for growth rates, ratios and returns.
Gibbs Free Energy Calculator (ΔG = ΔH − TΔS)Calculate Gibbs free energy change to predict whether a reaction is spontaneous at a given temperature.
Golf Score Differential Calculator (Handicap)Calculate a golf score differential from your adjusted score, course rating and slope rating — the basis of the World Handicap System.
Graham's Law Calculator (Effusion Rate)Compare effusion or diffusion rates of two gases from their molar masses using Graham's law — or find an unknown molar mass.
Grams to Cups Converter (Baking)Convert grams to US cups and cups to grams for flour, sugar, butter, rice, oats and other common ingredients.
Gratuity CalculatorCalculate gratuity from last drawn basic + DA and years of service using the 15/26 formula — with the ₹20 lakh tax-exempt limit.
Gravel & Aggregate CalculatorCalculate how much gravel, sand or crushed stone you need in m³, tonnes and cubic yards for a given area and depth.
Gravitational Force Calculator (Newton's Law of Gravitation)Calculate the gravitational force between two masses with F = Gm₁m₂/r² — from everyday objects to planets and moons.
GST Calculator (Add or Remove GST)Add GST to a price or remove GST from an inclusive amount. Shows CGST, SGST and the total at 5%, 18%, 40% and other GST rates.
Guntha to Sq Ft ConverterConvert guntha to square feet, square metres and acres — the land unit used in Maharashtra, Karnataka, Telangana and Gujarat.
Half-Life Calculator (Radioactive Decay)Calculate the amount remaining after radioactive decay — or the half-life or time elapsed.
Hardy–Weinberg Equilibrium CalculatorCalculate allele and genotype frequencies (p, q, p², 2pq, q²) from the frequency of the recessive phenotype.
Heart Rate Zone CalculatorFind your maximum heart rate and target heart rate for any training intensity using the Karvonen method.
Heat Conduction Calculator (Fourier's Law)Calculate heat flow through a wall, window or insulation layer using Fourier's law — with thermal conductivity, U-values and R-values.
Heat Duty Calculator (Q = ṁ·cp·ΔT)Calculate heating or cooling power from mass flow, specific heat and temperature difference — for heat exchangers, chillers and boilers.
Heat Sink Calculator (Thermal Resistance)Calculate the maximum heat sink thermal resistance for a transistor, MOSFET or regulator from power dissipation, junction and ambient temperatures.
Hemocytometer Cell Count CalculatorCalculate cells per mL from hemocytometer counts, squares counted and dilution — plus total cells.
Hooke's Law Calculator (Spring Force)Calculate spring force, spring constant or extension with Hooke's law (F = kx), plus the elastic energy stored in the spring.
Horizontal Tank Volume CalculatorCalculate liquid volume in a partially filled horizontal cylindrical tank from its level — and the level for a given volume.
Hourly to Salary CalculatorConvert an hourly wage to annual, monthly and weekly salary — or a salary back to an hourly rate.
Hours Worked Calculator (Time Card)Calculate hours worked from start and end time minus breaks — plus your pay for the shift.
HRA Exemption CalculatorWork out how much of your house rent allowance is tax-exempt under Section 10(13A) — metro and non-metro — and how much is taxable.
Hydraulic Cylinder Force CalculatorCalculate push and pull force of a hydraulic cylinder from pressure, bore and rod diameter — or the pressure for a required force.
Hydrostatic Pressure & Tank Level CalculatorConvert liquid level to hydrostatic pressure and pressure to level for any liquid density — ideal for level transmitter ranging.
Ideal Gas Law Calculator (PV = nRT)Solve the ideal gas law for pressure, volume, amount of gas (moles) or temperature.
Ideal Weight CalculatorEstimate ideal body weight from height using the Devine formula, plus the healthy BMI weight range for your height.
Inches to CM ConverterConvert inches to centimetres (and cm to inches) instantly, with charts for common sizes, heights and fractions of an inch.
Income Tax Calculator India (FY 2026-27, New vs Old Regime)Calculate income tax for FY 2026-27 under the new and old regime — with standard deduction, ₹12 lakh rebate, marginal relief, surcharge and 4% cess.
Induction Motor Slip and Synchronous Speed CalculatorCalculate synchronous speed, slip and rotor frequency of an induction motor from supply frequency, number of poles and rated speed.
Inductor Energy CalculatorCalculate the energy stored in an inductor's magnetic field from inductance and current with E = ½LI² — for chokes, relays and SMPS design.
Inflation CalculatorSee what today's money will cost in the future, or what a future amount is worth today, at any inflation rate.
Instrument Accuracy Calculator (% of Span vs % of Reading)Convert instrument accuracy between % of span, % of full scale and % of reading — and find the measurement error at any point in the range.
Instrumentation Amplifier Gain Calculator (Rg)Calculate the gain-setting resistor Rg for INA128, INA333, AD620 and other instrumentation amplifiers — or the gain from a given Rg.
Inverter Battery Backup CalculatorFind how many hours your inverter battery will run your load — or the battery Ah you need for a target backup time.
IV Drip Rate Calculator (gtt/min and mL/h)Calculate IV infusion rates in drops per minute and mL per hour from volume, time and drip factor — for nursing and clinical practice.
Kg to Lbs ConverterConvert kilograms to pounds and pounds to kilograms instantly — plus stone and ounces. Free online kg to lbs converter with formula and examples.
Kinetic Energy CalculatorCalculate kinetic energy from mass and speed (KE = ½mv²) — or the speed or mass from a known energy.
KM to Miles ConverterConvert kilometres to miles and miles to kilometres — for running, driving and travel distances. Free online KM to miles converter with formula and examples.
kVA to kW Converter (and kW to kVA)Convert kVA to kW and kW to kVA using power factor — for generators, UPS, transformers and DG set sizing.
KVP Calculator (Kisan Vikas Patra)Calculate Kisan Vikas Patra maturity — your money doubles in 115 months at the current 7.5% rate. See the maturity value for any amount.
kW to Amps Calculator (Single-Phase, Three-Phase and DC)Convert kilowatts to amps for single-phase, three-phase and DC circuits using voltage and power factor — with charts for 230 V and 415 V.
kW to HP Converter (Kilowatts to Horsepower)Convert kilowatts to horsepower and hp to kW for motors, engines, pumps and generators — mechanical hp and metric PS.
Law of Cosines CalculatorFind the third side, the angles and the area of any triangle from two sides and the included angle, using the law of cosines.
LC Resonant Frequency CalculatorCalculate the resonant frequency of an LC circuit — or the inductance or capacitance needed to tune to a frequency — for filters, oscillators and radios.
LDL Cholesterol Calculator (Friedewald)Estimate LDL cholesterol from total cholesterol, HDL and triglycerides using the Friedewald formula, plus non-HDL cholesterol and ratios.
League Points Calculator (Football / Soccer)Calculate league points, points per game and goal difference from wins, draws and losses.
Lean Body Mass CalculatorEstimate lean body mass (everything except fat) from height, weight and sex using the Boer formula.
LED Bulb Savings CalculatorCalculate energy, money and CO₂ saved by replacing old bulbs with LEDs. Free online LED bulb Savings calculator with formula and examples.
LED Resistor CalculatorCalculate the series resistor value and wattage for one LED or a string of LEDs from supply voltage, forward voltage and current.
Length ConverterConvert between metres, feet, inches, centimetres, kilometres, miles, yards and millimetres — type in any field.
Ligation Calculator (Insert : Vector Ratio)Calculate how many ng of insert to use for a ligation at a chosen molar ratio of insert to vector.
Line and Phase Voltage Calculator (Star and Delta)Convert between line and phase voltage and current for star (wye) and delta connections — with three-phase power from either.
Liquid Volume to Weight ConverterConvert millilitres or cups of water, milk, oil, honey and other liquids to grams — and back.
Liters to Gallons ConverterConvert litres to US or UK gallons and gallons to litres — for fuel, water tanks and liquids. Free online liters to gallons converter with formula and examples.
Loan Payment (EMI) CalculatorWork out the monthly payment (EMI), total interest and total cost of any loan — home, car or personal.
Logarithm Calculator (log, ln, log₂)Calculate logarithms in any base — log₁₀, natural log (ln), log₂ — or find the number from its logarithm.
Logistic Growth Calculator (Carrying Capacity)Model population growth that slows as it approaches the environment's carrying capacity (K). Free online logistic growth calculator with formula and examples.
LPG Gas Cylinder Duration CalculatorEstimate how many days an LPG gas cylinder will last from its weight and your daily cooking use.
Lumpsum Calculator (One-Time Investment)See how a one-time mutual fund investment grows over time — maturity value, gains and CAGR — or find the lump sum needed for a goal.
Macro Calculator (Protein, Carbs, Fat)Split your daily calories into grams of protein, carbohydrate and fat using your chosen macro percentages.
Magnification Calculator (Microscopy)Calculate magnification, image size or actual specimen size using image size ÷ actual size.
Margin of Error CalculatorCalculate the margin of error for a survey or poll from sample size, proportion and confidence level.
Mark–Recapture Population Estimator (Lincoln–Petersen)Estimate an animal population size from mark and recapture counts using the Lincoln–Petersen and Chapman methods.
Mass Flow Rate CalculatorConvert volumetric flow to mass flow and back using fluid density — kg/h, t/h, lb/h, m³/h, L/min and more.
Mass Percent (w/w) Concentration CalculatorCalculate mass percent concentration of a solution from solute and solvent mass — or the solute needed for a target percent.
Mean Arterial Pressure (MAP) CalculatorCalculate mean arterial pressure from systolic and diastolic blood pressure readings.
Mean, Median & Mode CalculatorFind the mean, median, mode and range of any list of numbers — paste data from a spreadsheet.
Meat per Person Calculator (BBQ & Parties)Calculate how much meat to buy for a barbecue or party based on the number of guests and appetite.
Meters to Feet ConverterConvert metres to feet (and feet and inches) instantly, with charts for heights, rooms and buildings.
Microscope Field of View CalculatorCalculate the diameter of a microscope's field of view from the eyepiece field number and objective magnification.
Miles to KM ConverterConvert miles to kilometres and km to miles instantly, with charts for running distances, speed limits and road trips.
ML to Oz Converter (Fluid Ounces)Convert millilitres to US fluid ounces and fl oz to mL instantly — for drinks, baby bottles, cosmetics and recipes.
MM to Inches ConverterConvert millimetres to inches (decimal) and inches to millimetres for engineering, tools and pipe sizes.
Molality CalculatorCalculate molality (mol/kg) from the mass of solute, its molar mass and the mass of solvent.
Molarity CalculatorCalculate molarity (mol/L), the mass of solute needed, or the solution volume for any substance.
Moles Calculator (Mass ↔ Moles ↔ Particles)Convert between grams, moles and number of particles using molar mass and Avogadro's number.
Momentum Calculator (p = mv)Calculate momentum from mass and velocity, or find velocity or mass from momentum.
Mortar Calculator (Cement & Sand)Calculate cement bags and sand needed for a given volume of mortar at any mix ratio, such as 1:4 or 1:6.
Mortgage CalculatorCalculate your monthly mortgage payment from home price, down payment, interest rate and term — plus total interest.
MOSFET Power Dissipation Calculator (Conduction and Switching Loss)Estimate MOSFET conduction and switching losses from Rds(on), current, voltage, switching frequency and rise/fall times — and the junction temperature.
Motor Starting Current Calculator (DOL, Star-Delta, Soft Starter)Estimate the starting (inrush) current of an induction motor for DOL, star-delta, autotransformer and soft-starter starting from full-load current.
MPH to KM/H ConverterConvert miles per hour to kilometres per hour (and km/h to mph) instantly, with speed-limit and driving charts.
Nernst Equation CalculatorCalculate the cell potential under non-standard conditions with the Nernst equation, from E°, electrons transferred, temperature and reaction quotient.
Net Run Rate (NRR) CalculatorCalculate a cricket team's net run rate for tournament standings from runs scored and conceded.
Normal Distribution Probability CalculatorFind the probability that a normally distributed value is below, above or between limits — from mean and standard deviation.
NPS Calculator (National Pension System)Estimate your NPS corpus at 60, the lump sum you can withdraw and the monthly pension from the annuity — using current exit rules.
NSC Calculator (National Savings Certificate)Calculate NSC maturity value and interest at the current 7.7% rate for the 5-year post office National Savings Certificate.
NTC Thermistor Calculator (Beta Equation)Calculate NTC thermistor resistance at any temperature, or temperature from resistance, using the beta (B) equation — for 10k, 100k and other thermistors.
Number to Million ConverterConvert any number to millions, billions, lakhs and crores instantly — or type in any field to convert the other way.
Odds to Probability ConverterConvert betting or statistical odds to probability and back — fractional odds, decimal odds and percentage chance.
Ohm's Law CalculatorEnter any two of voltage, current, resistance or power and get the other two — with steps, unit conversion and a live graph.
One-Rep Max (1RM) CalculatorEstimate your one-rep max from the weight and reps you can lift, with training percentages.
Op-Amp Gain Calculator (Inverting and Non-Inverting)Calculate the voltage gain and output of an inverting or non-inverting op-amp amplifier from Rf and Rin — or the resistor needed for a target gain.
Orbital Period Calculator (Kepler's Third Law)Calculate the orbital period and speed of a satellite or planet from the central mass and orbit radius — ISS, GPS, geostationary orbits and more.
Orifice Plate Flow CalculatorCalculate liquid flow through an orifice plate from differential pressure, bore, pipe size and density — or the DP for a given flow.
Osmotic Pressure CalculatorCalculate osmotic pressure from molarity, van 't Hoff factor and temperature using π = iMRT.
Ounces to Grams Converter (oz to g)Convert ounces to grams and grams to ounces instantly — for cooking, postage, jewellery and nutrition labels.
Oven Temperature Converter (°C, °F, Gas Mark)Convert oven temperatures between Celsius, Fahrenheit, gas mark and fan-oven settings.
Ovulation & Fertile Window CalculatorEstimate your ovulation date, fertile window and next period from your last period and cycle length.
P/E Ratio Calculator (Price to Earnings)Calculate the price-to-earnings ratio, earnings yield and PEG ratio of a stock from its share price, EPS and growth rate.
Pace to Speed Converter (Treadmill)Convert running pace (min/km or min/mile) to speed in km/h or mph — and back. Ideal for treadmills.
Pack-Year Calculator (Smoking History)Calculate smoking pack-years from cigarettes per day and years smoked — used to assess lung cancer screening eligibility.
Paint Calculator (Walls & Rooms)Calculate how much paint you need for a room from wall size, doors, windows, number of coats and coverage.
Paper Weight Calculator (GSM)Calculate the weight of paper sheets or a ream from GSM and paper size. Free online paper weight calculator with formula and examples.
Party Drinks CalculatorEstimate how many drinks, bottles and ice to buy for a party based on guests and hours. Free online party drinks calculator with formula and examples.
Password Strength (Entropy) CalculatorCalculate password entropy in bits and estimate how long it would take to crack by brute force.
Payback Period CalculatorCalculate how long an investment takes to pay for itself from yearly savings or cash flow — simple and discounted payback.
PCB Trace Width Calculator (IPC-2221)Calculate the PCB trace width needed for a current and temperature rise using the IPC-2221 formula — for external and internal layers and copper weights.
PCR Amplification CalculatorEstimate how many DNA copies a PCR produces from the starting copies, number of cycles and efficiency.
Pendulum Period CalculatorCalculate the period and frequency of a simple pendulum from its length — or the length for a given period.
Per-Unit System Calculator (Base Impedance and Base Change)Calculate base impedance, base current and per-unit impedance for power system studies — and convert per-unit values to a new base.
Percent Composition CalculatorCalculate the mass percent of an element in a compound from atom count, atomic mass and molar mass.
Percent Error CalculatorCalculate the percent error between a measured (experimental) value and the true (accepted) value.
Percent Yield CalculatorCalculate the percent yield of a chemical reaction from the actual and theoretical yield.
Percentage CalculatorFind what is P% of a number, what percent one number is of another, or the whole from a part — type in any two fields.
Percentage Change CalculatorCalculate the percentage increase or decrease between two values, or find the new value after a percentage change.
Permutation Calculator (nPr)Calculate the number of permutations — ordered arrangements of r items chosen from n.
PFDavg Calculator (SIL Verification, 1oo1)Calculate the average probability of failure on demand (PFDavg) for a 1oo1 safety function from dangerous undetected failure rate and proof test interval — with SIL band.
pH CalculatorConvert between pH, pOH, hydrogen ion and hydroxide ion concentration — with acidic or basic classification.
Pipe Flow Velocity CalculatorCalculate fluid velocity in a pipe from flow rate and inner diameter — or the flow rate and pipe size for a target velocity.
Pipe Pressure Drop Calculator (Darcy–Weisbach)Calculate friction head loss and pressure drop in a pipe from length, diameter, velocity and friction factor.
Pitot Tube Velocity CalculatorCalculate air or liquid velocity from pitot tube differential pressure — and the flow in a duct or pipe.
Pizza Size & Value CalculatorCompare two pizzas by area and price per square inch to see which one is the better deal. Free online pizza size & value calculator with formula and examples.
Poisson Probability CalculatorCalculate the probability of exactly k events in an interval when events occur at an average rate λ.
Pond Liner Size & Volume CalculatorCalculate the pond liner size you need and the pond's water volume from length, width and depth.
Population Density CalculatorCalculate population density (individuals per km², hectare or square mile) from count and area.
Post Office Monthly Income Scheme Calculator (POMIS)Calculate monthly income from the Post Office MIS at the current 7.4% rate, plus total interest over 5 years.
Potential Energy Calculator (PE = mgh)Calculate gravitational potential energy from mass and height — or the height for a given energy.
Pounds to Kilograms Converter (lbs to kg)Convert pounds to kilograms and kg to lbs instantly, with charts for body weights, luggage and gym plates.
Power Converter (kW to HP, BTU/h)Convert power between kW, W, horsepower (hp and metric PS), BTU/h and tons of refrigeration.
Power Factor Correction Calculator (Capacitor kVAr)Calculate the capacitor bank kVAr and capacitance needed to raise power factor from its present value to a target — with current reduction.
PPF Calculator (Public Provident Fund)Calculate PPF maturity value and interest for yearly deposits at the current 7.1% rate — including 5-year extensions after 15 years.
PPM Calculator (Parts per Million)Calculate concentration in ppm from solute and solution mass — and convert ppm to percent and mg/L.
Pregnancy Due Date CalculatorEstimate your baby's due date and how many weeks pregnant you are from the first day of your last period.
Pregnancy Weight Gain CalculatorSee the recommended total weight gain in pregnancy based on pre-pregnancy BMI, using the Institute of Medicine (IOM) 2009 guidelines.
Present Value CalculatorFind what a future amount is worth today (present value) at a given discount rate — or the future value of money today.
Pressure Calculator (P = F/A)Calculate pressure from force and area — or the force or area — in Pa, kPa, bar or psi.
Pressure ConverterConvert bar, psi, kPa, MPa, atm, mbar, mmHg, inH₂O and mH₂O — for instruments, tyres, hydraulics and weather.
Primer Melting Temperature (Tm) CalculatorEstimate a DNA primer's melting temperature from its base composition using the Wallace rule, and a suggested annealing temperature.
Print Size Calculator (Pixels & DPI)Calculate the maximum print size of an image from its pixel dimensions and print resolution (DPI/PPI).
Probability Calculator (Two Events)Calculate the probability of A and B, A or B, not A, and neither — for two independent events.
Profit Margin CalculatorCalculate profit, profit margin and markup from cost and selling price — or find the price for a target margin.
Projectile Motion CalculatorCalculate range, maximum height and flight time of a projectile from launch speed and angle. Free online projectile motion calculator with formula and examples.
Protein Concentration Calculator (A280)Calculate protein concentration from A280 absorbance using the molar extinction coefficient and molecular weight.
Protein Intake CalculatorWork out how many grams of protein you need per day based on body weight and activity or goal. Free online protein intake calculator with formula and examples.
Protein Molecular Weight EstimatorEstimate a protein's molecular weight in kDa from its number of amino acids. Free online protein molecular weight estimator with formula and examples.
PSI to Bar ConverterConvert psi to bar and bar to psi instantly — for tyres, compressors, hydraulics and pressure gauges.
Pt100 / Pt1000 Resistance CalculatorConvert RTD temperature to resistance and resistance to temperature for Pt100, Pt500 and Pt1000 sensors (IEC 60751, 0–850 °C).
Pulley Speed and Belt Length CalculatorCalculate driven pulley rpm, speed ratio, belt speed and belt length for two-pulley belt drives — or the pulley size for a target speed.
Pump Power CalculatorCalculate hydraulic power and shaft power of a pump from flow rate, head, fluid density and efficiency.
PWM Duty Cycle CalculatorCalculate PWM duty cycle, period, on-time and average output voltage from frequency and pulse width — for motor speed control, LEDs and microcontrollers.
Pythagorean Theorem CalculatorFind the hypotenuse or a missing side of a right triangle from the other two sides, in any length unit.
QTc Calculator (Corrected QT Interval)Calculate the corrected QT interval (QTc) from QT and heart rate using the Bazett, Fridericia, Framingham and Hodges formulas.
Quadratic Equation SolverSolve ax² + bx + c = 0 — get both roots and the discriminant with step-by-step working. Free online quadratic equation solver with formula and examples.
Quartile & IQR Calculator (Five-Number Summary)Calculate quartiles Q1, Q2, Q3, the interquartile range and outlier fences — the five-number summary for a box plot.
Race Time Predictor (Riegel Formula)Predict your finish time for a 5K, 10K, half marathon or marathon from a recent race result. Free online race time predictor with formula and examples.
Rainwater Harvesting CalculatorCalculate how much rainwater you can collect from a roof based on area, rainfall and runoff coefficient.
Ratio Calculator (Proportion Solver)Solve proportions A:B = C:D — enter any three values to find the fourth. Great for scaling recipes, maps and mixtures.
RC Filter Cutoff Frequency CalculatorCalculate the −3 dB cutoff frequency of an RC low-pass or high-pass filter, or the R or C needed for a target cutoff — with attenuation at any frequency.
RC Time Constant CalculatorCalculate the RC time constant, charging time and cut-off frequency of a resistor–capacitor circuit.
RD Calculator (Recurring Deposit)Calculate recurring deposit maturity and interest for monthly deposits with quarterly compounding — for banks and post office RD.
Reactance and Impedance Calculator (XL, XC and Z)Calculate inductive reactance, capacitive reactance and series RLC impedance at any frequency — with phase angle.
Reading Time CalculatorEstimate how long it takes to read (or speak) a text from its word count and reading speed. Free online reading time calculator with formula and examples.
Real Rate of Return Calculator (Inflation-Adjusted)Calculate your real return after inflation (and tax) from a nominal interest rate or investment return — see if your money is really growing.
Rebar Weight CalculatorCalculate the weight of steel reinforcement bars (rebar) from diameter, length and quantity. Free online rebar weight calculator with formula and examples.
Recipe Scaler (Servings Converter)Scale any recipe ingredient up or down for a different number of servings.
Rectangle Calculator (Area, Perimeter, Diagonal)Calculate a rectangle's area, perimeter and diagonal from length and width — or a missing side from the area.
Rectangular Tank Volume CalculatorCalculate the capacity of a rectangular or square water tank, sump or overhead tank in litres, m³ and gallons.
Regular Polygon Calculator (Angles, Area, Perimeter)Find the interior and exterior angles, number of diagonals, perimeter and area of any regular polygon — triangle, hexagon, octagon and more.
Relative Risk & Odds Ratio CalculatorCalculate relative risk, odds ratio and absolute risk difference from a 2×2 table of exposed and unexposed groups.
Rent Split Calculator (By Room Size)Split rent fairly between roommates based on bedroom size, with shared space divided equally. Free online rent split calculator with formula and examples.
Required Run Rate Calculator (Cricket)Calculate the runs per over needed to chase a target with the balls remaining. Free online required run rate calculator with formula and examples.
Resistor Color Code Calculator (4-Band)Find a resistor's value and tolerance from its 4 colour bands — or look up the colours for any resistance. Includes the full colour chart.
Resistors in Series & Parallel CalculatorCalculate total resistance of up to three resistors connected in series or in parallel.
Retirement Corpus CalculatorEstimate how much money you need at retirement based on today's expenses, inflation and a safe withdrawal rate.
Reynolds Number CalculatorCalculate the Reynolds number of pipe flow and see whether it is laminar, transitional or turbulent.
Rice to Water Ratio CalculatorFind how much water to use for white, basmati, jasmine, brown rice and more — by cups or grams.
Right Triangle Calculator (Trigonometry)Solve a right triangle from an angle and one side — find all sides and angles with sin, cos and tan.
RL Time Constant CalculatorCalculate the time constant τ = L/R of an inductor-resistor circuit, plus current rise and decay at any time — for relays, solenoids and filters.
ROAS Calculator (Return on Ad Spend)Calculate ROAS, ad profit and break-even ROAS from ad spend, revenue and margin — for Google, Meta and other paid campaigns.
ROI Calculator (Return on Investment)Calculate return on investment (ROI), gain and annualized return from the amount invested and the final value.
Roof Pitch CalculatorCalculate roof pitch as an angle, ratio (x:12) and percentage — plus rafter length — from rise and run.
Rule of 72 — Doubling Time CalculatorFind how many years it takes for money to double at any interest rate — exact result plus the Rule of 72 estimate.
Running Cadence & Stride Length CalculatorCalculate running speed from cadence and stride length — or the stride length from your pace and cadence.
Running Pace CalculatorCalculate running pace per km or mile, finish time or distance — enter any two.
Salary Increase CalculatorCalculate your new salary after a raise — or the percentage raise between two salaries — yearly and monthly.
Sales Tax / VAT / GST CalculatorAdd or remove sales tax, VAT or GST from a price — find the net price, tax amount and gross price in one step.
Sample Size Calculator (Surveys)Find how many survey responses you need for a given margin of error and confidence level — with finite population correction.
Savings Goal CalculatorFind how much to save each month to reach a savings goal — or how long it will take — with interest included.
Screen PPI Calculator (Pixel Density)Calculate pixels per inch (PPI) and dot pitch of a screen from its resolution and diagonal size. Free online screen PPI calculator with formula and examples.
SCSS Calculator (Senior Citizens Savings Scheme)Calculate quarterly interest and total returns from the Senior Citizens Savings Scheme at the current 8.2% rate — with the ₹30 lakh limit.
Serial Dilution CalculatorCalculate the final concentration after a series of dilution steps, and the total dilution factor.
Shower Water & Energy CalculatorCalculate how much water and energy your showers use — and what a low-flow head or shorter shower saves.
Signal-to-Noise Ratio (SNR) CalculatorCalculate signal-to-noise ratio in dB from signal and noise voltages or powers — with ENOB (effective number of bits) for ADCs.
Simple Interest CalculatorCalculate simple interest and total amount from principal, rate and time — or find the rate or time you need.
SIP Calculator (Monthly Investment)See how a fixed monthly investment (SIP) grows over time with compounding — or find the monthly amount for a target.
Sleep Calculator (Bedtime & Wake-Up Time)Find the best time to wake up or go to bed based on 90-minute sleep cycles.
Slope Calculator (Two Points)Find the slope, distance and angle of a line through two points — with step-by-step working.
Snell's Law Calculator (Refraction and Critical Angle)Calculate the angle of refraction, refractive index or critical angle when light passes between two materials, using Snell's law.
Solar Battery Storage Size CalculatorCalculate the battery capacity needed for backup or off-grid solar from daily load, autonomy days and depth of discharge.
Solar Panel Output CalculatorEstimate daily, monthly and yearly energy from a solar PV system based on size, sun hours and system losses.
Solar System Size CalculatorWork out the solar PV system size (kWp) and number of panels needed to cover your electricity use.
Specific Growth Rate Calculator (µ)Calculate the specific growth rate of a culture from two measurements, plus the doubling time.
Specific Heat Calculator (q = mcΔT)Calculate heat energy needed to change a substance's temperature — or the temperature change from added heat.
Speed Converter (km/h, mph, m/s, knots)Convert speeds between km/h, mph, m/s, ft/s and knots instantly — type in any field.
Speed, Distance & Time CalculatorCalculate speed, distance or travel time — enter any two and get the third, in km/h, mph, m/s, km or miles.
Sphere Calculator (Volume & Surface Area)Calculate sphere volume and surface area from radius or diameter — or the radius from volume.
Square Feet to Square Meters ConverterConvert square feet (sq ft) to square metres (m²) and back — for flats, houses, offices and flooring.
Square Footage & Cost CalculatorCalculate the area of a room or space in ft² and m² and the total cost at a price per unit area.
Square Meters to Square Feet Converter (m² to sq ft)Convert square metres to square feet and sq ft to m² instantly — for flats, rooms, plots and flooring.
Square Root CalculatorFind the square root, cube root and square of any number — with a table of perfect squares and simplified radicals.
Stair Calculator (Risers & Treads)Calculate the number of steps, riser height, total run and stair angle from the floor-to-floor height.
Standard Deviation CalculatorPaste your data to get sample and population standard deviation, variance, mean and count — with steps.
Standard Error of the Mean CalculatorCalculate the standard error of the mean (SEM) from your data — or from standard deviation and sample size.
Star-Delta (Y-Δ) Transformation CalculatorConvert delta (Δ) resistances or impedances to an equivalent star (Y), and star to delta — for circuit analysis and network simplification.
Steel Plate Weight CalculatorCalculate the weight of steel, stainless steel or aluminium plates and sheets from their dimensions.
Step-Up SIP Calculator (Top-Up SIP)See how increasing your SIP amount every year boosts your corpus. Compare step-up SIP vs regular SIP with total invested and returns.
Steps to Distance CalculatorConvert steps to kilometres or miles using your height — plus an estimate of calories burned walking.
Stock Average Calculator (Average Down Calculator)Calculate the average buy price of shares after buying at different prices — and how many more shares you need to reach a target average.
Stone to KG ConverterConvert stone (and stone and pounds) to kilograms and kg to stone instantly — the UK way of stating body weight.
Strain Gauge Calculator (ΔR and Bridge Output)Calculate the resistance change and Wheatstone bridge output of a strain gauge from gauge factor, strain and excitation — for quarter, half and full bridges.
Sugar to Honey Substitution CalculatorReplace sugar with honey or maple syrup in recipes — with the liquid reduction and oven adjustment.
Sukanya Samriddhi Yojana Calculator (SSY)Calculate Sukanya Samriddhi maturity at the current 8.2% rate — 15 years of deposits, maturity at 21 years, fully tax-free.
Sum of Squares CalculatorCalculate the total sum of squares (squared deviations from the mean) and the sum of squared values for a data set.
SUVAT Equations Calculator (Kinematics)Solve constant-acceleration motion problems — initial velocity, final velocity, acceleration, time and displacement.
Swim Pace Calculator (per 100 m)Calculate swimming pace per 100 m or 100 yd, total time or distance. Free online swim pace calculator with formula and examples.
SWP Calculator (Systematic Withdrawal Plan)Plan monthly withdrawals from a mutual fund corpus — see the balance left, total withdrawn and how long your money will last.
Temperature ConverterConvert between Celsius, Fahrenheit and Kelvin instantly — type in any field. Free online temperature converter with formula and examples.
Ten-Pin Bowling Average & Handicap CalculatorCalculate your bowling average and league handicap from total pins, games played and the league basis.
Test Score & Grade Percentage CalculatorConvert a test score to a percentage — and find the letter grade on a typical scale.
THD Calculator (Total Harmonic Distortion)Calculate total harmonic distortion (THD) of voltage or current from the fundamental and harmonic magnitudes, with IEEE 519 limits.
Thermal Expansion CalculatorCalculate how much a pipe, rail or bar expands with temperature for steel, stainless steel, aluminium, copper and PVC.
Thin Lens Equation Calculator (Lens and Mirror Formula)Find focal length, object distance, image distance and magnification for lenses and mirrors using 1/f = 1/dₒ + 1/dᵢ.
Three-Phase Motor Power & Current CalculatorCalculate input power, output power and full-load current of a three-phase motor from voltage, power factor and efficiency.
Tile Calculator (Floor & Wall)Calculate how many tiles you need for a floor or wall from the area and tile size — with grout gap and waste.
Time Duration CalculatorFind the time between two clock times in hours and minutes — works across midnight. Free online time duration calculator with formula and examples.
Tip Calculator (Split the Bill)Calculate the tip, total bill and amount per person when splitting a restaurant bill.
Titration CalculatorCalculate the unknown concentration of an acid or base from titration volumes and the mole ratio.
Torque Calculator (Force × Lever Arm)Calculate torque from force and lever length at any angle — or the force needed to reach a target torque with a spanner or wrench.
Torque Converter (N·m to lb·ft)Convert torque between N·m, kN·m, lbf·ft, lbf·in and kgf·m — for bolts, engines and motors.
Torque, Power & Speed CalculatorConvert between shaft power, torque and rotational speed (rpm) for motors, gearboxes and engines.
Transformer Current Calculator (Full-Load Amps)Calculate primary and secondary full-load current of single-phase and three-phase transformers from kVA and voltages.
Transformer Efficiency Calculator (Iron and Copper Losses)Calculate transformer efficiency at any load and power factor from no-load (core) and full-load (copper) losses — plus the load for maximum efficiency.
Transformer Short-Circuit Current CalculatorEstimate the maximum fault current on a transformer secondary from kVA, voltage and percentage impedance (infinite-bus method).
Transformer Size Calculator (kVA Rating from Load)Calculate the transformer kVA rating needed for your connected load from kW, power factor, diversity factor and future growth — and pick the next standard size.
Transformer Turns Ratio CalculatorCalculate transformer secondary voltage, turns ratio and primary or secondary current from the number of turns or voltages.
Transistor Base Resistor Calculator (BJT Switch)Calculate the base resistor for an NPN or PNP transistor used as a switch — from load current, hFE and drive voltage, with overdrive for saturation.
Trapezoid Area CalculatorCalculate the area of a trapezoid (trapezium) from its two parallel sides and height — or find a missing side.
Trees to Offset CO₂ CalculatorEstimate how many trees it would take to absorb a given amount of CO₂ per year. Free online trees to offset CO₂ calculator with formula and examples.
Triangle Area CalculatorCalculate the area of a triangle from its base and height, or find the height or base from the area.
Turkey & Roast Cooking Time CalculatorEstimate roasting time for turkey, chicken, beef, pork and lamb from weight — plus resting time.
Turkey Thawing Time CalculatorCalculate how long to thaw a frozen turkey in the fridge or in cold water based on its weight.
Turndown Ratio Calculator (Flow Meter Rangeability)Calculate the turndown ratio of a flow meter or control valve from maximum and minimum flow — and the minimum flow for a given turndown.
TV Size & Viewing Distance CalculatorFind a screen's width and height from its diagonal and aspect ratio — plus the recommended viewing distance.
Typing Speed Calculator (WPM)Calculate typing speed in words per minute (WPM) and characters per minute from your test results.
Ultrasonic Level Calculator (Time of Flight and Temperature)Calculate the distance and liquid level measured by an ultrasonic level transmitter from echo time and air temperature — with the speed-of-sound correction.
Unit Price Comparison CalculatorCompare two products by price per unit (per kg, litre or item) to find the better deal. Free online unit price comparison calculator with formula and examples.
UPS Size Calculator (kVA)Calculate the UPS kVA rating needed for your load from watts, power factor and a growth margin — for homes, offices, servers and control panels.
Venturi Meter Flow CalculatorCalculate liquid flow through a Venturi tube from the differential pressure, inlet and throat diameters — with permanent pressure loss.
Vertical Jump Height Calculator (Hang Time)Calculate vertical jump height from flight (hang) time — or the hang time for a given jump height.
Vertical Tank Volume Calculator (Level to Volume)Calculate the volume of liquid in a vertical cylindrical tank from its diameter and level — with full capacity, percentage fill and litres per mm.
VFD Braking Resistor CalculatorCalculate the maximum braking resistor value and average power rating for a VFD braking chopper from DC bus voltage, braking power and duty cycle.
Video File Size Calculator (Bitrate)Calculate video file size from bitrate and duration — or the bitrate for a target file size.
VO₂ Max Calculator (Cooper Test)Estimate your VO₂ max from the distance you can run in 12 minutes using the Cooper test.
Voltage Divider CalculatorCalculate the output voltage of a resistor voltage divider, or the resistor values needed for a target output — with divider current and power.
Voltage Unbalance Calculator (NEMA Method)Calculate percentage voltage unbalance from three line voltages, plus the motor derating and extra temperature rise it causes.
Volume ConverterConvert litres, gallons (US and UK), millilitres, cubic metres, cubic feet and cubic inches — type in any field.
Waist-to-Height Ratio CalculatorCalculate your waist-to-height ratio (WHtR), a simple measure of central body fat and health risk.
Waist-to-Hip Ratio CalculatorCalculate your waist-to-hip ratio (WHR) and compare it with WHO risk thresholds for men and women.
Wallpaper CalculatorEstimate how many rolls of wallpaper you need from room perimeter, wall height and roll size — including pattern repeat waste.
Water Hammer Calculator (Joukowsky Equation)Calculate the surge pressure from sudden valve closure or pump trip with the Joukowsky equation — with wave speed and critical closure time.
Water Heater (Geyser) Heating Time CalculatorCalculate how long an electric water heater takes to heat a tank of water — and the energy used.
Water Intake CalculatorEstimate how much water to drink per day based on your body weight and exercise time. Free online water intake calculator with formula and examples.
Water Leak (Dripping Tap) CalculatorEstimate how much water a dripping tap or leak wastes per day and per year. Free online water leak calculator with formula and examples.
Water Potential CalculatorCalculate solute potential and total water potential of plant cells or solutions (Ψ = Ψs + Ψp).
Wavelength & Frequency CalculatorConvert between wavelength, frequency and wave speed for light, radio and sound (v = fλ).
Weight Calculator (Mass to Weight on Planets)Convert mass to weight (force) on Earth, the Moon, Mars and other planets using W = m × g.
Weighted Average CalculatorCalculate a weighted average (weighted mean) from up to five values and weights — for grades, prices, portfolios and survey scores.
Weir Flow Calculator (V-Notch and Rectangular)Calculate open-channel flow over a V-notch or rectangular weir from the head — for effluent, irrigation and flow measurement.
Wheatstone Bridge CalculatorCalculate the output voltage of a Wheatstone bridge, or the unknown resistance at balance — for strain gauges, RTDs and sensor circuits.
Win Percentage CalculatorCalculate a team's or player's win percentage from wins, losses and ties.
Wind Turbine Power CalculatorCalculate wind turbine power from rotor diameter, wind speed, air density and power coefficient.
Wire Resistance Calculator (Copper and Aluminium)Calculate the resistance of a copper or aluminium wire or cable from length, cross-section and temperature — plus resistance per km.
Work & Power CalculatorCalculate work done (W = F × d) and power (P = W ÷ t) from force, distance and time. Free online work & power calculator with formula and examples.
Yeast Converter (Instant, Active Dry, Fresh)Convert between instant yeast, active dry yeast and fresh (cake) yeast amounts.
Z-Score CalculatorCalculate the z-score of a value from the mean and standard deviation — plus its percentile under a normal distribution.
Zener Diode Resistor Calculator (Voltage Regulator)Calculate the series resistor and power ratings for a Zener diode shunt regulator from input voltage, Zener voltage and load current.