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If an automatic watch that used to keep good time is suddenly running fast, the most likely cause is magnetism. A magnetized hairspring sticks to itself and the balance swings faster, so the watch can gain seconds or even minutes a day. Demagnetizing usually fixes it in minutes. If the watch is losing time instead, the usual cause is a low wind or a movement that needs service.
Before you fix anything, though, check that the watch is actually out of spec. Mechanical watches are never as accurate as quartz, and some daily variation is normal.
What is normal accuracy?
| Standard | Daily rate | Who sets it |
|---|---|---|
| COSC chronometer | -4 to +6 seconds per day (average, tested uncased) | Swiss chronometer testing institute |
| Rolex Superlative Chronometer | -2 to +2 seconds per day (after casing) | Rolex |
| Seiko 4R caliber (e.g. 4R36) | +45 to -35 seconds per day | Seiko |
| Typical quartz | About seconds per month | Most makers |
So a Seiko 5 that gains 15 seconds a day is within spec, while a chronometer that gains 30 seconds a day is not. Find your caliber's published tolerance in the manual or on the maker's site, and see our guide on how accurate automatic watches are for typical ranges.
How to measure your watch's rate properly
- Wind it fully by the crown, or wear it all day first. Our guide on how to wind an automatic watch covers the number of turns.
- Set it to an accurate reference, such as a time-sync website or your phone, to the second.
- Wear it normally for 24 hours, then compare. Note the difference.
- Repeat for several days. One day can be misleading; an average over three to seven days is meaningful.
- Try a timegrapher app for a quick read, but treat it as a rough guide. Phone microphones are less reliable than a watchmaker's timegrapher. Our guide to reading a timegrapher explains how to read the results.
Diagnose by symptom
| Symptom | Most likely cause | First thing to try |
|---|---|---|
| Suddenly gains many seconds or minutes a day | Magnetism | Demagnetize |
| Runs fast when not worn, fine on the wrist | Resting position | Change the overnight position |
| Loses time at night or when not worn | Low wind, resting position | Wind fully; change the position |
| Loses time while worn | Low wind (little arm movement) or a movement needing service | Wind fully each morning; then service |
| Erratic: fast one day, slow the next | Shock, low wind or worn oils | Wind fully; see a watchmaker if it continues |
| Gains in winter, loses in summer | Temperature | Normal within limits |
| Stops even when wound | Damage or dried oils | Service |
Cause 1: Magnetism (automatic watch running fast)
Seiko's guidance lists everyday magnetic sources: cell phones, TV and PC speakers, magnetic necklaces, handbag clasps, hair dryers, electric razors and refrigerator magnets. Add tablet covers, laptop lids, magnetic phone mounts and wireless chargers. Seiko also notes that a watch stays magnetized after you remove it from the source.
Magnetism makes the coils of the hairspring cling together, which effectively shortens it, so the balance swings faster and the watch gains. It is the most common cause of a sudden jump in rate.
Fix: have it demagnetized. Watchmakers do it quickly with a demagnetizer, and inexpensive demagnetizers exist for home use. We explain the process in how to demagnetize a watch. Then keep the watch a few inches away from the usual sources.
If you own several mechanical watches, a home unit pays for itself quickly; look for a US-plug model that comes with a compass so you can confirm the fix.
Cause 2: Resting position
Gravity affects the balance differently depending on how the watch lies. Seiko says the rate of a mechanical watch varies with position: dial up, dial down, or resting on the 12, 3, 6 or 9 o'clock side.
Fix: use it to your advantage. Seiko suggests leaving the watch in different positions for 7 to 8 hours when not in use and checking the gain or loss in each. If your watch gains on the wrist, store it overnight in the position where it loses, and vice versa. Every watch is different, so test yours.
Cause 3: Low wind (losing time)
As the mainspring runs down, it delivers less steady power, and accuracy suffers. Seiko recommends winding the mainspring every day at a fixed time, even on a self-winding watch, and wearing the watch for more than 8 hours a day.
A desk job is the classic trap: little arm movement, so the rotor barely winds the watch, which then runs in the weak end of its reserve. Our guide on automatic watch power reserve explains why the last hours of a reserve are the least accurate.
Fix: give it 20 to 30 crown turns each morning, or keep it on a winder set to the right turns per day and direction from our watch winder settings lookup.
Cause 4: Temperature
Seiko says mechanical watches tend to lose time at high temperatures and gain at low temperatures, because metal parts expand and contract. It advises against leaving a watch below 5°C or above 35°C (about 41°F and 95°F). A watch left on a cold windowsill overnight in winter can gain.
Fix: store it at room temperature. Small seasonal changes are normal.
Cause 5: Shock
Seiko recommends removing your watch for sports with strong impacts. A hard knock can shift the hairspring or knock the regulation out. If a watch changed rate right after a drop or a round of golf, shock is the likely cause.
Fix: if wearing and winding normally does not settle it within a few days, see a watchmaker.
Cause 6: The movement needs service
Oils dry and thicken over years, which typically makes a watch lose time, run erratically or stop with a reduced power reserve. A worn or dirty movement cannot be fixed by regulation alone.
Fix: a full service: cleaning, new oils, new gaskets and regulation. Intervals vary by maker; see how often to service an automatic watch.
A simple home routine for better accuracy
- Wind it at a fixed time each morning, even on an automatic, as Seiko recommends.
- Wear it for a full day when you can.
- Store it overnight in the position that offsets its daily error.
- Keep it a few inches away from phones, speakers, laptops and chargers.
- Log the error every day for a week. If the average is within the caliber's tolerance, the watch is healthy.
When to see a watchmaker
- After demagnetizing, the watch still gains or loses beyond its published tolerance.
- The rate changed after a drop or impact.
- The power reserve is much shorter than the maker's figure.
- It stops on the wrist or soon after a full wind.
- It has not been serviced in longer than the maker's recommended interval.
A watchmaker can measure the watch on a timegrapher in several positions and regulate it in one visit if the movement is healthy.
Common mistakes
- Judging accuracy after one day. Average several days.
- Opening the case to regulate it yourself. It risks dust and breaks water resistance.
- Assuming a winder fixes everything. It only helps when the cause is low wind.
- Leaving the watch next to a laptop, speaker or wireless charger every night.
- Expecting quartz accuracy. Check the tolerance for your caliber first.
FAQ
Why is my automatic watch suddenly running fast?
The most common cause is magnetism. If a watch that kept good time suddenly gains several seconds or minutes a day, a magnetized hairspring is likely. Phones, speakers, laptop and tablet covers, bag clasps and magnetic mounts are typical sources. A watchmaker can demagnetize it in minutes.
How many seconds a day is normal for an automatic watch?
It depends on the movement. COSC-certified chronometers must average -4 to +6 seconds a day in testing, and Rolex's own standard is -2 to +2 seconds after casing. Entry-level movements have wider tolerances: Seiko lists +45 to -35 seconds a day for its 4R calibers.
Why does my automatic watch lose time when I don't wear it?
Usually because the mainspring runs low. Off the wrist, nothing winds it, and as it approaches the end of its power reserve, timekeeping becomes less stable. Resting position also matters. Wind it fully and try storing it dial up or crown down overnight.
Can a watch winder fix a watch that runs fast?
No. A winder keeps the mainspring wound, which helps a watch that loses time from low wind, but it does not correct magnetism, damage or a movement that needs regulation or service.
Can I regulate my automatic watch myself?
Regulation means opening the case and adjusting the balance, so it is a job for a watchmaker. Opening the case also risks dust and breaks water resistance. Positional tricks, full winding and demagnetizing are the safe home fixes.