A mechanical watch contains only a certain amount of power reserve to power the functions of the watch before it stops. A fully wound automatic watch usually possesses between 36 and 42 hours of energy before it needs to be wound again. Certain automatic timepieces possess a power reserve of up to ten days. A manual-wind watch can have a reserve between 48 hours and 15 days. The power reserve indicator lets the wearer know how much energy the watch still has in the mainspring and the amount of time the movement can continue to run without requiring winding.

Types of Power Reserve Indicators

There are various different locations watch manufactures will place the power reserve indicator display. While the most common location is on the dial, this isn’t always the case. It is important to note that just because there isn’t an indicator on the dial, it doesn’t mean there is no power reserve. Depending on the watch, there may not be an indicator or it may be visible through the case-back. The four most popular power reserve indicator displays are shown below.