Frequency ⇄ Period Converter
Convert between frequency in hertz and period in seconds, with the result in every unit from mHz to THz and from s to ps.
Formulas
- Period T (seconds) = 1 ÷ frequency f (hertz)
- Frequency f (hertz) = 1 ÷ period T (seconds)
Frequency is how many times something repeats in one second, and the period is how many seconds one repetition takes. One hertz is one cycle per second.
The value you enter is first converted to hertz (or seconds), the reciprocal is taken, and the result is converted to each unit. The calculation uses exact fractions, so there is no floating-point error, and rounding happens only once when the result is shown. Conversions between units that are powers of ten, such as kHz and ms, are exact.
Units
- Frequency: THz (10¹² Hz), GHz (10⁹ Hz), MHz (10⁶ Hz), kHz (10³ Hz), Hz, mHz (10⁻³ Hz)
- Period: s (seconds), ms (10⁻³ s), µs (10⁻⁶ s), ns (10⁻⁹ s), ps (10⁻¹² s)
Examples
- 50 Hz = a period of 20 ms (one cycle of 50 Hz mains power).
- 60 Hz = a period of about 16.67 ms (16.666… ms, shown as 16.66667 with 7 significant digits, so a rounded value).
- 1 kHz = a period of 1 ms.
- 1 MHz = a period of 1 µs.
- 1 GHz = a period of 1 ns.
- A period of 4 ns = 250 MHz.
- A period of 2 s = 0.5 Hz = 500 mHz.
Zero, very small and very large values
- Zero is "not available". A frequency of 0 has an infinite period, and a period of 0 has an infinite frequency, which cannot be shown as a number.
- Very small and very large values are handled. You can enter up to 12 digits before the decimal point and 6 decimal places. If the result is below 0.000001 or 1015 or more, it is shown in scientific notation such as 6.213712e-7; it is never rounded to 0.
- Negative values cannot be entered. Commas are accepted only as thousands separators.
Notes
- This tool only converts between period and frequency units. To find the wavelength of a sound you also need the speed of sound, which depends on temperature. For note lengths in milliseconds and hertz from a tempo, see the BPM Delay Calculator.
- Rotational speed (rpm) and tempo (BPM) are different units. For rpm, see the RPM ⇄ rad/s Converter.
- For converting between time units such as milliseconds and seconds, use the Time Converter.
Frequently asked questions
What is the period of 60 Hz in milliseconds?
About 16.67 ms (1 ÷ 60 = 0.016666… seconds, shown as 16.66667 ms). It does not divide exactly, so it is a rounded value.
What is the period of 1 MHz?
1 µs (one microsecond): 1 ÷ 1,000,000 Hz = 0.000001 seconds.
What is the period of 0 Hz?
It cannot be written as a number (it is infinite). The tool shows "Not available".
Can this find the wavelength of a sound?
No. The wavelength of a sound needs the speed of sound as well. This tool only converts between frequency and period.