Estimate how long your automatic watch will keep running after you last wore or wound it. Includes activity level adjustment and turns-per-day (TPD) recommendations for popular movements.
Common values: Seiko 5 / NH35 ≈ 41h · ETA 2824 ≈ 38–42h · Rolex ≈ 70h · Grand Seiko ≈ 72h
Most automatic movements need a certain number of rotor turns per day to stay fully wound when worn.
If you are inactive (desk job), a watch winder set to the correct TPD direction can keep the watch running.
The calculator starts with your watch’s official power reserve, subtracts the hours that have already passed, then adjusts the remaining estimate based on how active you have been (because wrist movement partially rewinds the mainspring).
What is power reserve? It is the number of hours an automatic or mechanical watch can run when fully wound without any further movement or winding.
Does wearing the watch keep it wound? Yes. The rotor inside an automatic watch winds the mainspring through normal wrist movement. Higher activity keeps the watch closer to full power.
What is TPD? Turns Per Day – the approximate number of full rotor rotations needed in 24 hours to keep the watch fully wound.
Can I use this for manual-wind watches? Yes for the power reserve part. Just set activity level to the lowest option since there is no automatic winding.