Duty Cycle Calculator Formula
Understand the math behind the duty cycle calculator. Each variable explained with a worked example.
Formulas Used
Duty Cycle
duty_cycle_pct = on_time_us / period_us * 100Off Time
off_time = period_us - on_time_usFrequency
frequency = 1e6 / period_usDuty Ratio
duty_ratio = on_time_us / period_usVariables
| Variable | Description | Default |
|---|---|---|
on_time_us | On Time (Pulse Width)(µs) | 500 |
period_us | Total Period(µs) | 1000 |
How It Works
What is Duty Cycle?
Duty cycle is the fraction of one period during which a signal is in its active (high) state.
Formula
Duty Cycle = On Time / Period x 100%
Off Time = Period - On Time
Duty cycle is fundamental to PWM (Pulse Width Modulation), which controls motor speed, LED brightness, and power delivery by varying the on-time while keeping frequency constant.
Worked Example
A 1 kHz signal with 500 microsecond on-time.
- 01Duty cycle: 500 / 1000 x 100 = 50.0%
- 02Off time: 1000 - 500 = 500 microseconds
- 03Frequency: 1,000,000 / 1000 = 1000 Hz
Frequently Asked Questions
What is 50% duty cycle?
A square wave where the signal is high for exactly half the period. This is the most common starting point for PWM.
How does duty cycle relate to average voltage?
The average voltage equals duty cycle times the peak voltage: V_avg = Duty x V_peak.
Can duty cycle be over 100%?
No. Duty cycle ranges from 0% (always off) to 100% (always on). Values outside this range indicate an error in measurement.
Ready to run the numbers?
Open Duty Cycle Calculator