Saudi Luxury / Watch basics
Power reserve explained: how long a watch runs off the wrist
What a power reserve figure means in practice, so you can tell whether a mechanical watch will still be running after a weekend off.
Power reserve is how long a fully wound mechanical watch keeps running once you take it off or stop winding it. About 40 hours covers a night and the following day; 70 hours or more carries a watch through a two-day weekend.
The weekend test
Take a watch off on Thursday evening and pick it up on Sunday morning, and it has sat for about 60 hours. That sum splits watches into two groups.
The Citizen NJ0180-80X, a titanium automatic, is rated at 42 hours. It will have stopped by Saturday afternoon, and on Sunday you will need to set it again. The Hamilton Khaki Field H70455533 is rated at 80 hours, as is the Rado Coupole Classic R22861115, and the Rolex GMT-Master II 126710GRNR at 70. All three will still be running. If you wear a different watch at weekends, this decides whether your weekday watch is ready on Sunday.
Why the rating flatters
The figure assumes a full wind. An automatic worn by someone who spends the day at a desk may never reach one, because the rotor needs wrist movement to wind the mainspring. If yours stops sooner than its rating suggests, wind it by the crown before you put it on, where the movement allows hand-winding, and follow the maker’s instructions. Many mechanical watches also keep slightly less accurate time in their last hours, as the mainspring’s push weakens. If a watch that used to run its full reserve now stops early even after a full wind, it is due a service.
Very long reserves
A few hand-wound watches run for a week or more. The IWC Portofino IW510103 is rated at 192 hours, or eight days, and the Hublot Big Bang 414.NI.1123.RX at 240 hours. They suit a watch worn once a week, though you still have to remember to wind them. A longer reserve does not by itself mean better accuracy.
Rating or indicator
The hours on a spec sheet are a rating. A power-reserve indicator is a hand or window on the dial that shows how much wind is left now, most useful on a hand-wound watch. The site lists watches with a power-reserve indicator separately, and a watch without one may still have a long reserve. Watch Codex explains how power reserve is stored, shown and used.
Stopping, winding and winders
- Letting a mechanical watch stop does it no harm. Wind it, then set the time and, on a date watch, the date. Before setting a date, read how to set a calendar without damaging it.
- A healthy automatic cannot be overwound: once the mainspring is full, a slipping bridle in the barrel releases any extra winding. A hand-wound watch has no such slip, so turn the crown until you feel firm resistance, then stop. Never force it.
- A winder is a convenience, not a need. It earns its place mainly with watches that take time to reset, such as perpetual calendars and moonphases. Set its turns and direction to suit the calibre.
- Quartz and solar watches run for months or years without being worn, so the question hardly arises.