Watch WinderBasics
How accurate should a mechanical watch be?
Anywhere from a couple of seconds to half a minute a day, depending on the movement. A mechanical watch will never match quartz, and it doesn't need to: what matters is that it's consistent.
What's normal
| Grade | Typical spec |
|---|---|
| Entry-level automatics, such as the Seiko 4R and NH movements | −35 to +45 s/day |
| Standard Swiss movements | about ±12 s/day on average |
| COSC-certified chronometer | −4 to +6 s/day |
| Stricter in-house standards (Rolex, Omega, Grand Seiko and others) | within a few seconds a day |
These are the maker's tolerances, not a promise for any single day. Most watches do better than their spec when new and regulated, and drift a little between services.
Measuring your watch
- Wind it fully, then set it exactly to a reference such as time.gov or your phone's clock, ideally with the second hand stopped on a hacking movement.
- Wear it normally for 24 hours.
- Compare it to the same reference at the same time the next day. The difference is its daily rate.
- Repeat for a few days. The average is more telling than a single day.
Timegrapher apps that listen to the ticking through your phone's microphone give a rough reading in a minute, but they're easily fooled. The 24-hour test on the wrist is the one that counts. The accuracy calculator does the arithmetic and compares it with the spec.
Why it varies
- Position. Gravity pulls on the balance differently when the watch is dial up, dial down or on its side. A watch often gains in one position and loses in another.
- State of wind. Many movements run a little differently as the mainspring runs down. Accuracy is usually best in the first day after a full wind, one reason to keep watches topped up rather than running to empty.
- Temperature and how actively you wear it.
- Magnetism, if the change is sudden and large. See Is my watch magnetized?
Tricks that help
Use position to your advantage. Once you know how your watch behaves, you can rest it overnight in the position that cancels out the day's error. If it gains while you wear it, try leaving it crown down or dial down overnight; if it loses, try dial up. A few nights of testing tells you which works.
If the rate is well outside spec, or it has changed noticeably, a watchmaker can regulate it, usually quickly and without a full service. If it also runs short of its power reserve, it's probably time for a service.