# Buck Converter Calculator

URL: https://speedycalculator.com/calculators/physics/buck-converter/
Last updated: 2026-10-30

> The buck converter calculator finds the duty cycle and inductance of a step-down DC–DC converter from the input and output voltages, switching frequency and inductor ripple current.

## Inputs

- Input voltage V_in (V, mV, kV, µV, MV)
- Output voltage V_out (V, mV, kV, µV, MV)
- Switching frequency f_sw (kHz, MHz, Hz)
- Inductor ripple current ΔI_L (A, mA, µA, kA)
- Efficiency (%)

## Results

- Duty cycle D
- Inductance L

## Formula

```
D = V_out / (V_in·η),  L = (V_in − V_out)·D / (f_sw·ΔI_L)
```

## Explanation

Buck converters efficiently step down voltages – the 12 V to 1 V regulators that feed processors, or the USB chargers in cars. Unlike linear regulators, they waste little power as heat.

### How to use the Buck Converter Calculator

- **Input voltage V_in**
- **Output voltage V_out**
- **Switching frequency f_sw**
- **Inductor ripple current ΔI_L**
- **Efficiency (%)**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the input and output voltages, the switching frequency, the ripple current and the efficiency.

### Inputs explained

FieldWhat to enterInput voltage V_inUnits: V, mV, kV, µV, MVOutput voltage V_outUnits: V, mV, kV, µV, MVSwitching frequency f_swUnits: kHz, MHz, HzInductor ripple current ΔI_LUnits: A, mA, µA, kAEfficiency (%)A number

### What each result means

- **Duty cycle D** = [Output voltage V_out]÷([Input voltage V_in]×[Efficiency (%)]÷100)×100
- **Inductance L** = ([Input voltage V_in] - [Output voltage V_out])×[Output voltage V_out]÷([Input voltage V_in]×[Efficiency (%)]÷100)÷([Switching frequency f_sw]×[Inductor ripple current ΔI_L])

### Example values

How the main result changes when **Input voltage V_in** changes and everything else stays at the example values above:

Input voltage V_in (V)Duty cycle D (%)690.5797960.38651245.28991536.23191830.19322422.6449

## Worked example

Inputs — Input voltage V_in: 12 V; Output voltage V_out: 5 V; Switching frequency f_sw: 500 kHz; Inductor ripple current ΔI_L: 0.6 A; Efficiency (%): 92.

Results — **Duty cycle D = 45.2899 %**; Inductance L = 10.56763 µH.

## Key terms

- **Step-down converter**: Another name for a buck converter.

## FAQ

**Why are buck converters efficient?**
The switch is either fully on or off, so it dissipates little power.

**What does ripple current affect?**
Output voltage ripple and core losses.

**Can D exceed 100%?**
No – the output can't exceed the input.

**How do I choose the frequency?**
Higher frequencies allow smaller inductors but increase switching losses.


## Sources

- [Texas Instruments – Power supply design application notes](https://www.ti.com/power-management/overview.html)
- [OpenStax – University Physics Volume 2](https://openstax.org/details/books/university-physics-volume-2)