Why is my watch running fast or slow?
The usual causes of a mechanical watch gaining or losing time, from magnetism to a low mainspring, how to tell which it is, and what each fix costs.
Published
First, measure it
A feeling that a watch is fast is not a number. Measure it over a few days and compare the result with what is normal. Many watches that feel off are within spec.
Gaining minutes a day, suddenly
Almost always magnetism. The coils of the hairspring stick together and the watch races. Laptops, phone cases, bag clasps and speakers are the usual culprits. Test and fix it: demagnetising takes a watchmaker under a minute.
Gaining a lot after a knock
A hard knock can tangle the hairspring so that one coil catches on another, and the watch runs very fast or erratically. Unlike magnetism, a demagnetiser does not help. A watchmaker can usually free it without a full service.
Losing time, more as the day goes on
The mainspring is running low. A mechanical watch keeps its best time when well wound and slows as the spring runs down. Wind it in the morning, or wear it more. If it loses even when fully wound, the power reserve has dropped and it may need a service.
A few seconds that vary day to day
Normal. Rate changes with position, temperature and how active you are. Choosing how it rests overnight, dial up or crown down, can cancel out a few seconds a day.
Steady, but more than you like
A watch that gains or loses the same amount every day can be regulated. A watchmaker adjusts the balance in a few minutes, often for much less than a service. Ask them to check it on a timegrapher first.
Quartz watches
A quartz watch that suddenly loses time usually has a flat battery. Many signal it first: the seconds hand starts jumping in two- or four-second steps.