Crest Factor

Formula

Description

The crest factor is the ratio of the peak value to the RMS value of a waveform, indicating how extreme the peaks are relative to the average power. A pure sine wave has a crest factor of √2 (about 1.414), while a square wave has a crest factor of 1. Music and speech signals typically have crest factors of 4-10 (12-20 dB), meaning the peaks are much higher than the average level. Audio amplifiers and power supplies must handle these peaks without clipping, even though the average power draw is much lower.

Variables

• CF — Crest factor (dimensionless ratio)
• V_peak — Peak voltage (V)
• V_rms — RMS voltage (V)

Practical Notes

Crest factor is important for amplifier headroom design. A system with 10 dB crest factor needs an amplifier capable of 10× the average power to handle peaks cleanly. Audio compression reduces crest factor, making signals louder at the expense of dynamics. In power engineering, high crest factors in current waveforms indicate harmonic distortion that stresses transformers and wiring.