Boiling Point Elevation Calculator
By Santaji GadepatilinUpdated October 27, 2026
Dissolving a solute raises a liquid's boiling point by an amount that depends on how many particles are dissolved. It is one of the colligative properties of solutions. This free boiling point elevation calculator solves for whichever value you leave blank and shows the formula and steps.
How to use the boiling point elevation calculator
Choose the solvent, enter the van ’t Hoff factor, the molality and the solvent’s normal boiling point. The calculator gives the rise in boiling point and the new boiling point.
Boiling point elevation formula
ΔTb = i × Kb × m
Salt in water
| Salt (g per kg water) | Boiling point rise (ideal) |
|---|---|
| 5 g | 0.088 °C |
| 10 g | 0.175 °C |
| 30 g | 0.526 °C |
| 58.44 g | 1.024 °C |
| 100 g | 1.752 °C |
| 200 g | 3.504 °C |
Even very salty water boils only a degree or two above 100 °C.
Boiling point and altitude
| Altitude | Approximate boiling point of water |
|---|---|
| Sea level | 100 °C |
| 1,000 m | 96.7 °C |
| 2,000 m | 93.4 °C |
| 3,000 m | 90.0 °C |
| 5,000 m | 83.3 °C |
Pressure cookers raise the pressure so water boils at about 120 °C, speeding up cooking.
Molar mass from boiling point
Ebullioscopy works like cryoscopy: m = ΔTb ÷ (i × Kb), then molar mass = mass of solute ÷ (m × kg of solvent). Freezing point depression is usually preferred because the effect is larger.
Colligative properties
Freezing point depression, boiling point elevation, vapour pressure lowering and osmotic pressure all depend on the number of dissolved particles, not their identity.
Frequently asked questions
Does adding salt to pasta water make it boil hotter?
Only slightly. A tablespoon of salt (about 18 g) in 4 litres of water raises the boiling point by less than 0.1 °C. Salt is for flavour.
What is the ebullioscopic constant?
Kb, the boiling point rise for a 1 mol/kg solution of a non-dissociating solute. For water it is 0.512 °C·kg/mol.
Why is boiling point elevation smaller than freezing point depression?
Because Kb for most solvents is smaller than Kf. For water, Kf is 1.86 but Kb is only 0.512.
Does altitude affect boiling point?
Yes, much more than solutes do. Water boils at about 95 °C at 1,500 m and about 90 °C at 3,000 m because air pressure is lower.