Why is your automatic watch running fast or slow?

A few seconds fast or slow can tell you a lot about your watch. Find out what affects the accuracy of an automatic watch and when it’s actually worth paying attention.

You put your watch on in the morning, get on with your day and don’t think about the time again until a few days later. Then you compare it with your phone and there’s the surprise: thirty seconds fast. Or twenty seconds slow. The first reaction is usually inevitable: is there something wrong with my watch?

Probably not. In fact, those few seconds tell a much more interesting story. While your phone checks an electronic time reference, inside an automatic watch there are gears, springs, wheels and a tiny regulating organ working non-stop. Understanding why it can gain or lose time is also a great way to look at mechanical watchmaking from a different perspective.

Is it normal for an automatic watch to run fast or slow?

Yes. Pretty much every mechanical watch has a small daily variation, usually measured in seconds per day. What counts as normal depends on the movement, how it has been regulated and the standards set by each manufacturer.

So finding that your watch gains or loses a few seconds a day doesn’t automatically mean there’s a problem. As a reference, mechanical movements certified as chronometers by COSC have to pass a series of tests and maintain an average daily rate within specific limits of between −4 and +6 seconds per day.

A good example is the Ball Engineer M. Its in-house Ball RRM7309-C automatic calibre is COSC-certified and offers a power reserve of around 80 hours. But there’s one important thing to remember: a movement without COSC certification isn’t necessarily inaccurate. There are plenty of excellent calibres regulated according to each manufacturer’s own standards.

So why does accuracy change?

At the heart of the movement are the balance wheel and hairspring. Together they make up a large part of the regulating organ: a kind of tiny metronome that constantly oscillates and allows time to be divided into regular intervals. The problem — or, really, the beauty of it — is that we’re dealing with mechanics. And mechanics react to what’s happening around them.

1. The position of your watch matters more than you might think

Gravity has a slight effect on the way a mechanical movement works. A watch can behave differently when it’s on your wrist, lying dial-up on a table or resting overnight on its crown side.

That’s why more accurate movements are regulated in different positions. Your watch might even gain a little time while you wear it during the day and lose some of those seconds again while resting overnight. The position you leave it in at night can actually become a useful little trick for getting to know your watch better.

And this isn’t limited to classic, sporty or tool-style watches. Both the in-house calibre inside the Ball Engineer M and the well-known SW 200-1 found in models such as the Sinn 556 I use a mechanical regulating system, so both respond to those small positional variations that are simply part of how an automatic watch behaves.

2. Power reserve also plays a part

An automatic watch gets its energy from the movement of your wrist. As your arm moves, the rotor spins and helps wind the mainspring, where the energy that keeps the calibre running is stored.

When that reserve gets significantly lower, the amplitude of the balance wheel can change, which can slightly affect the watch’s rate. So if you want to check your watch’s accuracy, it’s best to do it when it has plenty of charge and monitor it over several days rather than just a few hours.

This also shows just how different two automatic watches can be. The Timex Atelier Marine M1a, powered by the Swiss automatic Catena SA 100 movement, offers around 36 hours of power reserve. The Citizen Tsuyosa 60 collection stretches that to 60 hours, while some models from the U-Boat Classico collection reach around 62 hours. The Ball Engineer M we mentioned earlier goes all the way up to 80 hours.

That doesn’t necessarily mean one figure is “better” than another. What matters is knowing the power reserve of your movement and understanding how it fits the way you actually wear your watch. If you rotate several watches throughout the week, for example, a longer power reserve can make a very practical difference.

3. Magnetism: the invisible enemy

This is where things get especially interesting. We’re surrounded by devices capable of generating magnetic fields: speakers, computers, tablets, magnetic clasps and all kinds of electronic accessories. If certain parts of the movement become magnetised, the behaviour of the watch can change quite noticeably.

A common sign is when a watch that used to keep a steady rate suddenly starts running much faster than usual. The good news is that, if magnetism is the cause, a watchmaker can usually demagnetise the movement fairly easily.

That’s exactly why some brands build specific anti-magnetic solutions into their watches. The Sinn 556 I, for example, offers magnetic resistance of 4,800 A/m. Move to an even more extreme construction and the Ball Engineer Hydrocarbon Original takes that protection up to 80,000 A/m.

Two very different watches that reveal something we usually can’t see: a watch case doesn’t just protect the movement from visible knocks and impacts, but also from forces that are completely invisible.

4. What if the watch has taken a knock?

Modern movements are designed to cope with everyday life, but they’re still made up of incredibly small components. A hard impact can affect the regulation or damage one of those parts.

The key here is to look at the before and after. If your watch used to keep a steady rate and suddenly starts behaving very differently just after a knock, it’s worth having it checked.

There are some really interesting technical solutions in this area too. The Sinn 556 I is rated for impact resistance up to 5,000 G, while the Ball Engineer Hydrocarbon Original reaches 7,500 G and features the patented SpringLOCK® anti-shock system. These figures give you an idea of just how far engineering can go when a watch is designed for particularly demanding conditions.

How to check how fast or slow your watch is running

You don’t need any special tools. Synchronise your watch with an accurate time reference, wait 24 hours and note the difference. Then repeat the process for several days.

Imagine that after five days your watch has gained 30 seconds. The maths is simple: 30 seconds ÷ 5 days = +6 seconds per day. That average is much more useful than checking the rate over just a few hours, because it gives you a much clearer picture of how the movement normally behaves.

And the nice thing is that this little test works just as well for getting to know an everyday Citizen Tsuyosa as it does for a Timex Atelier, a Sinn, a U-Boat or a COSC-certified Ball movement. Rather than comparing watches with each other, it’s about discovering the normal rhythm of your own watch.

When should you start paying attention?

Rather than chasing a perfect number, pay attention to sudden changes. If your watch has been gaining four or five seconds a day for months and suddenly starts gaining forty, then there’s a good reason to look into it.

A large, irregular or unusual deviation may be linked to magnetism, a need for regulation, ageing lubricants or simply the fact that it’s time for a service.

Imperfection is part of mechanical watchmaking too

A mechanical watch is unlikely to compete with a smartphone or a good quartz watch when it comes to absolute accuracy. And, oddly enough, maybe it doesn’t need to.

Inside a space just a few centimetres wide, dozens of tiny parts turn the energy stored in a spring into a constant measurement of passing time, without relying on a screen or an electronic connection. That tiny margin of a few seconds is also the signature of a machine that feels alive on your wrist.

So the next time you notice that your automatic watch is running slightly fast or slow, don’t immediately assume something is wrong. Watch it for a few days. You might not be looking at a fault at all. You might simply be discovering its own rhythm.

One mechanical heart, many different ways to experience it

And that’s exactly one of the most fascinating things about exploring the world of automatic watches: the same mechanical principle can sit behind completely different philosophies.

A Citizen Tsuyosa 60 brings a 60-hour power reserve to a watch designed to fit effortlessly into everyday life. A Timex Atelier Marine M1a approaches automatic watchmaking through a sporty Swiss Made aesthetic. U-Boat Classico pairs automatic calibres with an unmistakably Italian personality. Sinn takes the conversation towards functionality and durability, while Ball Engineer M focuses on chronometry, engineering and its in-house calibre.

Understanding what’s going on inside the case also changes the way we choose a watch. Once you know what power reserve, chronometer certification or a certain level of magnetic resistance actually mean, you stop looking only at the dial. You start discovering the watch behind the watch.

Have questions? Looking for a personalised recommendation? If you need any help, contact us and we’ll be happy to help.