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Duty cycle describes what fraction of a repeating pulse signal's cycle is spent "on" — a core concept behind PWM (pulse-width modulation), used to control everything from motor speed to LED brightness. This calculator solves for whichever value — pulse width, period, or duty cycle — is missing.
How it works
Enter any 2 of the 3 values (pulse width/on-time, period, or duty cycle) and leave the one you want to solve for blank. The calculator applies D = (tₒₙ/T) × 100.
- Enter pulse width / on-time (ms) — leave blank to solve for this.
- Enter period (ms) — leave blank to solve for this.
- Enter duty cycle (%) — leave blank to solve for this.
- Click Calculate to see your results.
Examples
A PWM dimming signal
A signal that's "on" for 3 ms out of every 10 ms period has a 30% duty cycle — useful, for example, for dimming an LED to 30% of its full brightness.
Who should use it
- Electronics and embedded systems coursework on PWM.
- Designing motor speed control, LED dimming, or similar PWM applications.
Industry applications
- Electronics and embedded systems
- Motor control and power electronics
Advantages
- Solves for any of the three variables, not just forward duty-cycle calculation.
- Directly applicable to real PWM design and analysis.
Limitations
- Assumes an idealized rectangular pulse — real signals have finite rise/fall times not captured here.
Common mistakes to avoid
- Confusing period (the full cycle length) with pulse width (just the "on" portion) — duty cycle is the ratio between them, not either one alone.
- Mixing time units (e.g. entering pulse width in microseconds but period in milliseconds) without converting to the same unit first.
Best practices
- Keep pulse width and period in the same time unit before entering them.
- Remember duty cycle alone doesn't tell you the signal's frequency — you need the period (or its reciprocal) for that.
Tips
- If you know the desired output frequency, convert it to a period first (T = 1/f) before solving for pulse width from a target duty cycle.