Boost Converter Calculator (Inductor and Capacitor)
By Santaji GadepatilinUpdated October 27, 2026
A boost converter steps a DC voltage up — for example from a 5 V USB supply to 12 V — by storing energy in an inductor and releasing it at a higher voltage. See the boost converter working principle and the related SEPIC converter.
How to use the boost converter calculator
Enter the input and output voltage, output current, expected efficiency, switching frequency, inductor ripple and allowed output ripple. You get the duty cycle, input current, inductance, peak switch current and minimum output capacitance.
For more background, read PFC Circuit: Boost Power Factor Correction.
The formulas (continuous conduction)
| Quantity | Formula |
|---|---|
| Duty cycle | D = 1 − Viη ÷ Vo |
| Input current | Ii = VoIo ÷ (Viη) |
| Inductance | L = Vi D ÷ (f ΔI) |
| Output capacitance | C = Io D ÷ (f ΔV) |
Example
5 V to 12 V at 0.5 A, 90% efficiency, 500 kHz, 30% ripple:
- D = 1 − 4.5 ÷ 12 = 62.5%
- Input current = 6 ÷ 4.5 = 1.33 A
- ΔI = 0.4 A, L = 5 × 0.625 ÷ (500,000 × 0.4) = 15.6 µH → use 15–22 µH
- Peak switch current = 1.53 A
- For 50 mV ripple, C ≥ 0.5 × 0.625 ÷ (500,000 × 0.05) = 12.5 µF
Design checks
- The switch and diode must handle the full output voltage plus spikes.
- Inductor saturation current must exceed the peak current.
- A boost converter has no short-circuit protection by itself — current flows straight from input to output through the inductor and diode.
- At very light loads the converter enters discontinuous mode, and the formulas above no longer apply.
Related topologies
- Buck-boost and SEPIC give an output above or below the input.
- PFC boost stages in power supplies shape input current to follow the mains voltage.
Frequently asked questions
What is the duty cycle of a boost converter?
D = 1 − V_in × η ÷ V_out. Boosting 5 V to 12 V at 90% efficiency needs a duty cycle of about 62.5%.
How much input current does a boost converter draw?
I_in = V_out × I_out ÷ (V_in × η). 12 V at 0.5 A from 5 V at 90% efficiency draws about 1.33 A.
How high can a boost converter step up?
Practically about 5–8 times. Very high duty cycles cause large losses and control problems.
Why is the output ripple larger than a buck's?
The output capacitor alone supplies the load while the switch is on, so the output current is pulsed.