Convert Frequency and Number per Time

Examples: a heart beats 75 times in one minute. It then has a frequency of 1.25 Hertz.

Alternating current has a frequency of 50 Hertz. So it changes its polarity 2000 times in 40 seconds.

Hz = hertz, kHz = kilohertz, MHz = megahertz, s = seconds, min = minutes, h = hours
1 Hz = 1/s = 60/min = 3600/h
1kHz = 1000 Hz, 1 MHz = 1000 kHz = 1000000 Hz

Frequency can be used for any phenomenon that recurs regularly. In the case of alternating current in the example above, this can be very regular, in contrast to the heartbeat, which of course can change its frequency quite often. In this case, the frequency determined is an average value over a certain period of time.
Frequency is an important parameter of electromagnetic radiation and can reach values ​​from a few hertz for extremely low-frequency radio waves to several exahertz for cosmic gamma radiation. Exa stands for quintillion, i.e. ten to the power of eighteen. Visible light is in the range 384 (red) to 789 (violet) terahertz, tera is trillion, ten to the power of twelve. Light and other electromagnetic radiation consists of waves and so the frequency indicates how often a wave crest (or wave trough, it doesn't matter which, but only one of the two) is passed through in one second. The distance between two wave crests or wave troughs is called the wavelength. Frequency and wavelength are therefore directly related; to convert, you only need the speed of light at which these waves move. For those further interested in this topic, see electromagnetic spectrum, where also calculations with such very large values ​​can be carried out.

Physics commonly uses SI units. Here is a calculator to convert units.