The kilohertz (kHz) equals 1,000 hertz, commonly used to describe audio frequencies, radio broadcasting bands, and early computer processor speeds. Human hearing ranges from about 20 Hz to 20 kHz, making this unit essential in audio engineering and music production. One kilohertz equals 1,000 cycles per second.

Revolutions per minute (rpm) measures rotational speed, expressing how many complete turns an object makes in one minute. It is the most common unit for engine speed, hard drive spin rates, and power tool specifications worldwide. One rpm equals exactly 1/60 hertz or approximately 0.01667 Hz.