Electronics · Free Calculator
PWM Duty Cycle Calculator
Find the duty cycle, average and RMS voltage of a PWM signal from its frequency and on time or duty cycle.
Duty cycle %Average voltageRMS voltageOn and off time
V
Duty cycle25.00 %
Average voltage3 V
RMS voltage6 V
On time250 µs
Off time750 µs
Period1 ms
How this result was calculated
- D = ton ÷ T = 250 µs ÷ 1 ms = 25.00 %
- Vavg = D × V = 3 V
- Vrms = √D × V = 6 V
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PWM Formulas
D = ton ÷ T = ton × f
Vavg = D × Vhigh
Vrms = √D × Vhigh
Vavg = D × Vhigh
Vrms = √D × Vhigh
Worked example
A 1 kHz, 12 V PWM signal with 250 µs on time has D = 25 %, an average of 3 V and an RMS value of 6 V.
Key insight: a resistive heater responds to RMS (power ∝ D), while a DC motor or LED responds roughly to the average, so the same duty cycle gives different results.
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Frequently Asked Questions
How do I calculate PWM duty cycle?
Divide the on time by the period and multiply by 100.
What is the average voltage of a 50 % PWM at 24 V?
12 V.
What PWM frequency should I use?
Above 20 kHz to make motors silent; 200 Hz to 1 kHz is enough for LED dimming without visible flicker.
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Pulse width modulation and duty cycle
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