Answer
Why is my watch running slow?
Short answer
Most slow watches are simply underwound: an automatic on a quiet desk day never reaches full wind, and the weak end of the mainspring loses time. After that, the usual causes are aging or dried lubricant, low amplitude from friction or wear, magnetism, and a resting position that loses. Steady, small losses are just regulation.
On this page (6 sections)
Losing time is the more diagnostic of the two failure directions. A watch that gains is usually mistimed or magnetized. A watch that loses is often short of energy, and energy problems have physical causes: not enough winding, thickened oil, added friction, wear. Work through the list in this order, because the first item is free and explains a large share of cases.
Low power reserve: the free explanation
A mechanical watch keeps its best time near full wind. As the mainspring unwinds, torque falls, the balance swings less far, and the rate drifts. This is a real property of every spring-driven oscillator, and it is why almost every published accuracy figure carries the words "at full wind".
An automatic depends on your arm to stay there. A day at a keyboard, a day driving, or a weekend of leaving the watch on a dresser can leave it running on the weak last third of its reserve, where losses of five or ten seconds a day are ordinary rather than faulty. A watch with a 40-hour reserve that you wear 12 hours a day and rest overnight can drift steadily downward across a week.
Aging or dried lubricant
A movement holds a few milligrams of oil and grease in perhaps a dozen places, and those lubricants degrade. They oxidize, migrate away from where they were placed, and thicken. Every one of those effects adds friction, and friction takes energy from the balance.
The signature is a loss that grows slowly over months or years rather than appearing overnight, often alongside a widening spread between positions. Typical service intervals run roughly five to ten years for a modern watch, and a movement that has never been serviced in fifteen years and is now losing 20 seconds a day is behaving exactly as expected. Our guide to servicing and care covers what the work involves.
Low amplitude, whatever the cause
Amplitude, the swing of the balance in degrees, is the number that separates a regulation problem from a repair. A healthy movement reads roughly 270 to 310 degrees dial up at full wind. Below about 250 degrees at full wind, something is wrong, and below roughly 200 degrees the watch is also at risk of stopping when left still.
Low amplitude has several causes: degraded oil, a tired or set mainspring, worn pivots, a bent balance staff, or debris in the train. They all present the same way from outside, which is why this is where home diagnosis stops and a bench begins.
Magnetism
Magnetism is best known for making watches gain, because magnetized hairspring coils cling together and shorten the spring. It can also slow a watch down: a magnetized steel part elsewhere in the movement, or a rotor or barrel that has picked up a field, adds drag rather than shortening the spring.
Because demagnetizing is quick, harmless to a mechanical movement, and usually free at a watchmaker, it is worth doing for an unexplained loss even though the odds are lower than for a gain. Our magnetism guide covers what fields do and which everyday objects produce them.
Wear pattern: it may not be the watch
Two owners can get different rates from the same watch. Rate varies by position, commonly across a 5 to 15 second a day spread, so somebody who sleeps with the watch crown up gets a different weekly average from somebody who leaves it dial up. Desk-bound days wind an automatic less than active ones. Cold weather changes the rate slightly. And measuring at 7 a.m. one day and 10 p.m. the next introduces error larger than the effect being measured.
Rule this out by measuring properly for seven days at the same time each day against an internet-synced clock, noting the overnight resting position. The accuracy calculator turns those readings into a mean daily rate, and our guide to timing your own watch explains what to record alongside them.
Matching the symptom to the fix
| Pattern | Likely cause | Fix and typical cost |
|---|---|---|
| Loses more on quiet days, fine on active days | Underwinding | Hand-wind daily, or wear it more. Free |
| Steady loss of 5 to 15 seconds a day, always has | Rate set slow | Regulation, roughly $60 to $150 |
| Loss growing gradually over months or years | Aging lubricant, friction | Service, roughly $250 to $800 depending on caliber |
| Runs when worn, stops overnight | Very low amplitude | Service |
| Loss appeared suddenly with no impact | Magnetism or debris | Demagnetize first, then bench diagnosis |
| Loss appeared after a drop | Displaced hairspring or damaged pivot | Watchmaker |
Treat those cost bands as indicative rather than quotes. They are US dollars before sales tax, which varies by state, and what you actually pay moves with local labor rates and with the choice between a brand service center and an independent watchmaker. Readers outside the US should expect their own figures to differ again, because import duty, local distribution and taxes all feed into bench prices. Ask for a written estimate, and treat any number here as a starting point rather than a quote. One last piece of perspective. A modern automatic that loses five seconds a day is inside most manufacturers' published tolerances and is not broken. The losses worth chasing are the ones that are large, growing, or accompanied by a watch that will not run through the night.
Common follow-up questions
How many turns of the crown should I give an automatic that keeps losing time?
Around 30 to 40 turns of the crown will take most automatics from stopped to close to full wind. You cannot overwind a modern automatic: the mainspring slips at the barrel wall once it is full. Hand-winding is the quickest way to test the underwinding theory, because if a week of full winds fixes the loss, the watch was never faulty.
Can a watch winder fix a slow watch?
Only if the cause is underwinding on days you do not wear it. A winder keeps a watch running and wound, which stabilizes the rate for a watch that would otherwise sit at low wind. It does nothing for dried oil, wear or magnetism, and it will not make a worn movement keep better time.
My watch loses time only when I am asleep. Is that a fault?
No, that is positional variation. Left overnight in one orientation for eight hours, the watch runs at that position's rate rather than the mixed average of a day of wear. If the overnight loss is larger than you want, rest it in a different position and re-measure for a week.
Is a slow watch worse than a fast one?
Mechanically, yes, slightly. Standards allow more gain than loss because losing time is more often a sign of energy being lost to friction, while a small gain is not. A persistent and growing loss is the more common early symptom of a movement that is due for a service.
Sources and further reading
- ISO 3159, Timekeeping instruments: wrist-chronometers with spring balance oscillator, for rate measurement across positions, temperatures and states of wind.
- Contrôle Officiel Suisse des Chronomètres (COSC), published certification criteria including mean daily rate and variation in rates.
- Witschi Electronic, timing machine documentation on amplitude, lift angle and the interpretation of rate and amplitude together.
- Donald de Carle, Practical Watch Repairing, for mainspring torque, isochronism and the effects of lubricant degradation.
- Movement manufacturers' technical data sheets (ETA, Sellita, Seiko), which publish power reserve, lift angle and rate tolerances.
Last reviewed 4 September 2026. Spotted an error? Tell us and we will fix it in public.