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Frequency / Period Calculator

Enter either the frequency or the period — leave the other field blank to calculate it.

Formula

  • f = 1 / T
  • T = 1 / f

f is frequency in hertz and T is the period in seconds. They are reciprocals of each other: frequency says how many cycles happen per second, period says how long one cycle takes, so a higher frequency always means a shorter period — a 1 kHz signal repeats every 1 ms, a 1 GHz signal every 1 ns.

About this calculation

Frequency and period are reciprocals of each other: a waveform that repeats every T seconds has a frequency f = 1 / T hertz, and a waveform repeating f times a second has a period of 1 / f. The calculator converts either way and handles the prefixes (Hz, kHz, MHz; µs, ms, s), so a datasheet figure in one form can be read in the other without moving decimal places by hand.

Assumptions and limits

  • The waveform is assumed periodic and at a steady frequency; modulated or drifting signals have neither a single period nor a single frequency.
  • The period is the time for one complete cycle, and the frequency counts cycles per second — the conversion is exact for both, including for mains and for clock oscillators.
  • It does not model rise time or duty cycle: a square wave's period is not the same as the time it spends high.

A worked example

A 50 Hz mains sine wave repeats every 1 / 50 = 0.02 s = 20 ms, while a 1 kHz tone repeats every 1 ms — the same two numbers, one upside down.

See also Nyquist Sampling and RC Time Constant.