PWM Duty Cycle Calculator Formula

Understand the math behind the pwm duty cycle calculator. Each variable explained with a worked example.

Use the PWM Duty Cycle Calculator

Formulas Used

Average Voltage

v_average = v_amplitude * duty_fraction

Average Power

avg_power_w = pow(v_amplitude, 2) * duty_fraction / load_resistance_ohm

Peak Current

peak_current_a = v_amplitude / load_resistance_ohm

Variables

VariableDescriptionDefault
v_amplitudePWM Amplitude(V)12
duty_cycle_pctDuty Cycle(%)75
load_resistance_ohmLoad Resistance(Ω)10
duty_fractionDerived value= duty_cycle_pct / 100calculated

How It Works

PWM Duty Cycle

Formulas

V_avg = V_amplitude x D

P_avg = V^2 x D / R

Where D is the duty cycle (0 to 1). PWM is used for motor speed control, LED dimming, and switching power supplies.

Worked Example

12 V PWM at 75% duty cycle driving a 10 ohm load.

v_amplitude = 12duty_cycle_pct = 75load_resistance_ohm = 10
  1. 01D = 75 / 100 = 0.75
  2. 02V_avg = 12 x 0.75 = 9 V
  3. 03P_avg = 144 x 0.75 / 10 = 10.8 W
  4. 04Peak current = 12 / 10 = 1.2 A

Ready to run the numbers?

Open PWM Duty Cycle Calculator