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Buck Converter Calculator

Find buck converter duty cycle, inductor ripple and peak current, output voltage ripple, and input current from your switching parameters.

SI prefixes accepted: 500k = 500 kHz, 10u = 10 µH,10m = 10 mΩ. Results assume continuous conduction mode — the calculator warns if your design falls into discontinuous mode.
Duty cycle–
Inductor ripple current ΔI_L–
Ripple as % of I_out–
Peak inductor current–
Output ripple — capacitive–
Output ripple — from ESR–
Output ripple — total–
Average input current–
Conduction mode–
V_inSWLV_out
Switch, inductor and catch diode; the output cap smooths the ripple

How a buck converter is sized

A buck (step-down) converter switches the input on and off rapidly and filters the result with an inductor and capacitor. Because it stores and releases energy rather than burning the difference as heat, it is far more efficient than a linear regulator at large step-downs.

Duty cycle: D = V_out / (V_in × η)

Inductor ripple: ΔI_L = (V_in − V_out) × D / (f × L)

Output ripple: ΔV_out = ΔI_L / (8 × f × C)

A common design target is inductor ripple around 20–40 % of the output current. Too little ripple means a bulky inductor; too much raises peak current and output noise. The peak inductor current (I_out + ΔI_L/2) is what the inductor's saturation rating and the switch must handle — size those on the peak, not the average.

The output-ripple figure assumes an ideal capacitor. Real capacitors add ripple through their ESR (roughly ΔI_L × ESR), which often dominates with electrolytics — ceramics are much better here.

Related

Compare against a linear regulatorfor the same rails, or use theinductor series & parallelcalculator to reach a target inductance.

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