Automatic Watch Power Reserve Calculator – Remaining Runtime
Last fully wound or taken off the wrist? Estimate hours left and when it may stop—before you find a dead seconds hand in the morning.
How to read the result
- Claimed reserve is catalogue energy from full wind, not a guarantee after a quiet day
- Taking the watch off starts a countdown from whatever was really stored
- Desk days often leave less than the marketing number
- If it dies early often, service, magnetism, or a tired mainspring may be involved
A 70-hour watch can still stop overnight if it was only partly wound when you set it down.
Educational model only — not a sensor inside your movement. Real rate of rundown varies.
Frequently Asked Questions
Typical automatic reserve? Many common calibers \~38–42 h; some modern designs \~70 h+.
Does wearing always keep it full? Active wear helps; low-motion days may not top up fully.
Stopped overnight? Often partial wind, shorter real reserve, or low activity—not always a broken watch.