Hertz (Hz)

Definition

The SI unit of frequency, one cycle per second.

History

The hertz is the SI unit of frequency, one cycle per second, named after Heinrich Hertz, who first produced and detected radio waves in the 1880s. It replaced the older term cycles per second.

Where it is used

Hertz measure screen refresh rates, audio pitch and the frequency of mains electricity.

Typical uses include refresh rates, audio, mains power.

Conversion pages

These pages convert hertz to or from another unit in frequency.

• Hertz to kilohertz

Other Frequency units

• Kilohertz (kHz)
• Megahertz (MHz)
• Gigahertz (GHz)
• Revolution per minute (rpm)

Sources

• BIPM SI BIPM SI Brochure (2019); ISO 80000-3 · Dataset reviewed Nov 11, 2026