Amplitude

Amplitude is how far the balance wheel swings in each oscillation, measured in degrees, and it's one of the main indicators of a mechanical movement's health.

Healthy amplitude suggests good power delivery and lubrication; low amplitude often points to a movement that needs servicing or a weakening mainspring. It varies with the watch's position and state of wind.

A timegrapher reads amplitude in seconds. Low readings on a pre-owned watch are a good reason to budget for a service before resale.