Clock Duty Cycle Calculator

Duty cycle is everywhere in electronics. Digital clocks typically run at 50% for balanced rise/fall timing. PWM signals span 0-100% for variable control of motors, LEDs, and switching regulators. Servo signals use extreme duty cycles (5-10%) in a fixed 50Hz period.

Beware of asymmetric duty in digital clocks: a 30/70% duty cycle still has the right frequency, but setup/hold margins are cut in half on one half-cycle. Clock synthesizers and crystal oscillators always output near 50% duty for this reason.

The concept of a duty cycle predates electronics — it originated in steam-engine terminology of the 1800s, describing the fraction of a piston stroke during which steam was admitted. The term migrated to electrical machinery in the 1900s (motor duty cycles: continuous, short-time, intermittent), then to pulse electronics during WWII radar development. Radar PRF (pulse repetition frequency) and duty cycle directly governed average transmitter power and range ambiguity.

Digital clock signals converged on ~50% duty in the 1970s as TTL became dominant. Setup and hold times specify how long data must be stable before and after a clock edge; asymmetric duty effectively shortens one of those windows. Modern DDR4 memory actually uses both edges (dual-edge triggering) for 2× data rate, making clock duty accuracy a first-class signal-integrity parameter — typical DDR4 spec is 45-55%.

PWM for power control exploded in the 1980s with the MOSFET revolution: switching an FET at 20-100 kHz with variable duty lets a DC bus drive motors, LEDs, solenoids, and power supplies with near-zero switch loss. Today PWM dominates drive electronics from million-volt rail traction inverters to milliamp phone vibrator motors.

Enter any two of: frequency, period, duty cycle, tHigh, tLow. The tool solves for the rest using T = 1/f, D = tH/T, tL = T − tH. Units with SI prefixes parse automatically (kHz, MHz, µs, ns). The waveform visualization shows one period at scale with the on/off windows marked.

Common gotchas: servo signals use 20 ms period (50 Hz) with 1-2 ms pulse width, which is 5-10% duty — not a 5 Hz signal. LED PWM should stay above ~200 Hz to avoid visible flicker for moving eyes; 1 kHz is a safe default. Motor PWM typically runs 16-25 kHz (above hearing). Everything runs client-side; no values leave your browser.