# What Is the Amplitude Equation for a Wave?

**The amplitude formula for a wave is amplitude (a) = distance traveled by the wave (d) / frequency of the wave (f).** The amplitude is the maximum height observed in the wave. Amplitude is measured in decibels (dB).

Amplitude (a) of a wave is how big the wave is or the energy of the wave. It is measured by the depth from the equilibrium point to the lowest point of a trough or the height from the equilibrium point to the highest point of a crest. The trough is the part of the wave that slopes downward, and the crest is the part of the wave that points upward.

Wavelength (d) is the length of a wave from one crest to another or from one trough to another. It is measured in metres.

The frequency (f) measures how many waves are passing a point per second and is the inverse of time. Frequency is measured is Hertz (Hz). The frequency is derived by 1 / T where T is the period of time. For example: if a pendulum takes 5 seconds to swing back and forth, then frequency is 1 divided by 5.