Buck Converter Calculator

What Is a Buck Converter?

A buck converter is a DC-DC step-down topology. A switch chops the input and an LC filter averages the output to a lower voltage. Duty cycle controls how much energy reaches the load each switching period.

Buck Converter Formulas

$$V_{\text{out}} = D \times V_{\text{in}}$$ $$D = \frac{V_{\text{out}}}{V_{\text{in}}}$$

$D$ is duty cycle (0 to 1), $V_{\text{in}}$ is input voltage, and $V_{\text{out}}$ is average output voltage in continuous conduction mode with ideal components.

Example: 12 V input with $D = 0.5$ gives 6 V output. To get 5 V from 12 V, $D = 5/12 \approx 0.417$.

Related tools: Voltage Converter and Power Converter.

Frequently Asked Questions

What is duty cycle?

It is the fraction of each switching period the MOSFET is on. 50% duty means the switch is closed half the time.

Can output exceed input?

No in a buck converter. Step-up requires a boost topology. Buck output is always less than or equal to input (ignoring losses).

Does this include efficiency losses?

This calculator uses the ideal CCM relation. Real designs lose voltage to switch resistance, diode drop, and inductor DCR.

What mode is assumed?

Continuous conduction mode (CCM), where inductor current never reaches zero. Light loads may enter DCM and need a different model.

Where are buck converters used?

CPU power rails, battery-powered devices, LED drivers, and anywhere a stable lower DC voltage is needed from a higher bus.

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What Is a Buck Converter?

Buck Converter Formulas

Frequently Asked Questions

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