Buck Converter Duty Cycle Calculator

Enter the input and output voltages to get the duty cycle.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

A buck (step-down) converter is a switch-mode power supply topology that steps a DC input voltage down to a lower DC output. In continuous-conduction mode with ideal (lossless) components, the output is set purely by the switch's duty cycle D: D = Vout/Vin, the fraction of each switching period the transistor spends on, since the inductor's average voltage over a cycle must be zero at steady state.

Power-electronics engineers use this formula as the starting point for setting the PWM duty cycle on a buck regulator IC — used everywhere from USB-C chargers to point-of-load regulators on a PCB that step 12V or 5V rails down to 3.3V or 1.8V for a microcontroller or SoC — before layering on real-world losses from switch resistance and diode drop.

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