Free tool to estimate how long your automatic or mechanical watch will keep running after you last wore or wound it. Enter the power reserve of your watch and when you last used it to get an accurate remaining time.
Common values: Seiko 5 ≈ 41h · Rolex ≈ 70h · Omega ≈ 60–72h · Grand Seiko ≈ 72h · Longines ≈ 64–72h
Automatic and mechanical watches store energy in a mainspring. The power reserve is the number of hours the watch can run when fully wound. Once you stop wearing or winding the watch, the remaining power gradually decreases until it stops.
This calculator subtracts the time that has passed since you last fully wound or wore the watch from its total power reserve and shows you how much runtime is left.
What is power reserve on a watch? Power reserve is the amount of time a mechanical or automatic watch can continue running after it has been fully wound, without additional winding or wrist movement.
How accurate is this calculator? It gives a very good estimate based on the official power reserve of your watch and the exact time since last full wind. Real-world results can vary slightly due to temperature, position, and remaining torque.
Does wearing the watch recharge it? Yes. An automatic watch recharges through the motion of your wrist. If you wear it daily, it usually stays fully wound.
What if my watch has a longer power reserve (like 80 hours)? Simply enter the correct number of hours in the field above. The calculator works with any power reserve from 20 to 1000+ hours.