Automatic watch running fast or slow: what is still normal
Before you worry that your automatic watch is running fast or slow, it is worth looking at the normal guide values. Unlike a quartz watch, which runs accurate to the second for practical purposes, a mechanical movement always has some deviation; that is in the nature of the technology. The recognised guide value is the COSC standard for certified chronometers: it allows an average deviation between minus 4 and plus 6 seconds per day.
Most automatic watches carry no chronometer certificate and may therefore deviate more. Many good, uncertified movements lie at roughly plus or minus 5 to 20 seconds per day as a guide, and that too is perfectly acceptable. More important than the absolute value is consistency: a watch that gains a steady five seconds every day is healthier than one that sometimes gains and sometimes loses. Only when the deviation is permanently far above these guide values or suddenly increases sharply is action needed.
Magnetism: the most common cause of running strongly fast
If an automatic watch suddenly runs noticeably fast, often by several seconds or even minutes per day, magnetism is by far the most common cause. The fine balance spring in the movement can become magnetically charged, so that its coils stick together. As a result the balance oscillates faster, and the watch runs fast. In everyday life, magnetic sources lurk everywhere: speakers, tablet covers with a magnetic closure, fridge doors, handbags with a magnetic clasp or laptop lids.
The good news is that magnetism is easy to fix. A watchmaker demagnetises the watch with a suitable device in a few minutes, after which it usually runs normally again straight away. How to recognise and avoid magnetism is explained in detail in our guide Magnetised watch: how to recognise and demagnetise it. So before you take a watch that runs strongly fast for regulation, magnetism should always be ruled out first, because it is the simplest and cheapest explanation.
Insufficient power reserve: the most common cause of running slow
If the watch runs slow instead, especially when it is taken off at night or at the weekend, an insufficient power reserve is usually to blame. The mainspring of an automatic watch is wound by movement on the wrist, and if it is not wound sufficiently, the amplitude of the balance drops. A falling amplitude means that the watch oscillates more slowly and loses time; the movement literally runs down.
If you wear the watch only a few hours a day or take it off overnight, the mainspring often does not get enough movement to hold the full power reserve. The remedy is to wind it fully by the crown or to use a watch winder, which keeps the watch moving even when it is at rest. The basics are explained in the guides Power reserve explained and Winding an automatic watch correctly. So if your watch runs slow after a rest period, first check whether it runs more accurately with a full power reserve.
Positional dependence and amplitude
A mechanical movement does not run the same in every position, and that is completely normal. Depending on whether the watch lies flat, stands on its crown or hangs vertically, gravity acts differently on the balance wheel, and the rate changes by a few seconds. Watchmakers therefore regulate good movements in several positions, so that the deviations balance out as far as possible over the day.
For you, this means two things. First, your watch may run differently on your wrist than on the bedside table at night, because it rests there in a particular position. If you choose a position at night that offsets the daytime rate, you can even reduce the overall deviation. Second, positional dependence explains why a single measurement says little: only the average over several days and different positions shows how your watch really runs.
Temperature, shocks and overdue service
External influences also affect timekeeping accuracy. Strong temperature fluctuations slightly change the properties of the balance spring, which is why a watch may run minimally differently in high summer than in winter, although modern materials have greatly reduced this effect. Hard shocks, such as a fall or a heavy blow, can briefly throw the balance wheel out of rhythm or, in the worst case, damage parts.
Perhaps the most important and often overlooked cause is an overdue service. The lubricating oil in the movement ages over the years, becomes viscous and increases friction, which shows up first as declining amplitude and thus poorer timekeeping accuracy. A movement that has not been serviced for years therefore often runs slow even though magnetism and power reserve are fine. As a rough guideline, an overhaul every five to seven years is often cited; the exact intervals are specified by the manufacturer. If all simpler causes have been ruled out, an overdue service is the most likely explanation.
Cause, identification and remedy at a glance
The following table summarises the most common causes and assigns each a typical identifying feature and the appropriate first measure. It does not replace a diagnosis by the watchmaker, but it helps you classify your own watch correctly before you take further steps.
| Cause | Typical sign | First remedy |
|---|---|---|
| Magnetism | sudden, strong gaining | have it demagnetised |
| Power reserve too low | losing time after rest periods | wind fully, use a watch winder |
| Positional dependence | different rate depending on night-time position | choose a favourable resting position |
| Temperature, shocks | temporary deviation after an event | normalise conditions, observe |
| Overdue service, old oil | persistent losing of time with no other cause | overhaul by the watchmaker |
| Regulation | constant deviation above the guideline value | fine regulation by the watchmaker |
The table shows a pattern: gaining points more towards magnetism, losing time more towards power reserve or service. This rule of thumb is not a guarantee, but it is a good starting point for the self-check in the next section.
Self-check in steps: how to find the cause
Before you go to the watchmaker, you can narrow down the cause yourself in a few steps. It is important to measure patiently, because a single reading says too little. It is best to allow a few days and note the deviation every morning at the same time against an accurate time source.
- Measure over several days in the same position: Wear the watch as usual and always place it in the same position at night. Note the deviation over three to five days, so you can see whether it consistently gains or loses.
- Wind fully: Wind the watch fully by the crown so that the power reserve is secured. If it runs noticeably more accurately afterwards, too little winding was the cause.
- Check different positions: On individual nights, place the watch in different positions, for example flat and on the crown. This shows you how strongly the rate depends on position and which resting position is favourable.
- Rule out magnetism: If the watch gains a lot, have it demagnetised or check it with a compass app as a rough indication. If the gaining disappears afterwards, magnetism was the reason.
- Interpret the result: If the deviation is within the guideline range after these steps, everything is fine. If it remains well above it, a regulation or service is due.
This structured procedure often saves the trip to the watchmaker, because many cases are already solved by fully winding or demagnetising. You can find further background on the mechanics in the watch knowledge section of TopWatchReviews.
When you need the watchmaker
There are clear cases in which a visit to the watchmaker is unavoidable. If the deviation remains persistently well above the guideline values after the watch has been fully wound and magnetism ruled out, only fine regulation helps: the watchmaker adjusts the effective length of the balance spring so that the watch runs within tolerance again. This work is routine and cannot be replaced by winding or a watch winder.
Likewise, a watch belongs in expert hands if the deviation suddenly increases sharply, appears after a fall or is accompanied by unusual noises. Persistent losing of time with no other identifiable cause also points to old oil and an overdue service. The watchmaker can demagnetise, regulate, check the servicing needs and, if in doubt, open the movement. If you are unsure whether the effort is worthwhile, you will find further guides on care and handling of automatic watches in our knowledge section.
The role of the watch winder: what it can and cannot do
A widespread misconception is that a watch winder can improve timekeeping accuracy or correct a watch that gains. That is not the case, and it is important to say so honestly. A watch winder keeps the automatic watch in motion and so ensures that the mainspring stays tensioned and the power reserve stays stable. That is precisely how it prevents losing time caused by too little winding, but nothing more.
What a winder cannot do is regulate the movement. If your watch gains or loses despite a full power reserve, this is due to the movement's adjustment, and only the watchmaker can change that, not a different winder or a different rotation speed. What matters, however, is that the winder delivers the right number of turns per day for your calibre, so that the watch actually stays fully wound. You will find the suitable values in the guide Turns per day, and our watch winder buying guide shows which devices handle this properly. That way the power reserve stays stable, while regulation stays where it belongs: with the specialist.