How to test the accuracy of your mechanical watch?

Hello Watchie.  Whether you own one precious watch or a whole collection, it is nice to know that your they are running to time accurately. If they are not, it may be time for a service. A tell tale sign is if your watch is running slow.

So, how can you check?

The good news is that there are some pretty neat ways to test your watch – with pretty good accuracy too.

If you are a the proud owner of a current mobile phone (apple or android) there are a couple of decent apps that I use.

I like HAIRSPRING. It will set you back a few quid and you need a half decent pair of ear buds to accompany the testing, but it is fun and good.


I also really enjoy Toolwatch – a Swiss company that offers a great web-app and mobile-app

Heres a bit of blurb….

About Toolwatch
Toolwatch is the most convenient and easy way to measure the accuracy of your mechanical watch.
Accuracy has always been the holy grail of watchmaking. Throughout the ages, watchmakers have been competing for building the most accurate and precise watch movement but the consumers do not have the tools to appreciate that effort. Now, with Toolwatch, every watch enthusiast is able to keep an eye on the accuracy of his watch(es)!

Why using Toolwatch?
Professional tools used by watchmakers are expensive (Toolwatch is free!) and heavy (Toolwatch is light!) and measure the watch in different positions (up, down, on a side etc) that do not reflect the actual way the watch is worn by its possessor. With Toolwatch, the accuracy is measured following your lifestyle. Unlike measuring by yourself, Toolwatch calculates for you the accuracy of your watch anytime and anywhere in an easy to use and reliable way.

How it works?
Toolwatch synchronizes your browser with the U. S. Naval Observatory’s atomic clocks cluster which produces a weighted average of several commercial atomic frequency standards. It is dominated by six active hydrogen masers, there are also a number of commercial cesium beam-tube standards in the cluster. We also account for the networking time between you and Toolwatch’ servers.
To put it simply, we do not use your computer clock but the most accurate atomic clock on earth to synchronize your timepieces.

The Toolwatch Team
Toolwatch is Swiss made with love!
We are three watch aficionados, passionate about mechanical watches, and willing to share our watchmaking enthusiasm.

We’ve worked inside the most prestigious watchmaking Manufactures in Switzerland and are happy to provide the best watch experience for enthusiasts all around the world.

Watch accuracy : how to read the1 results?

So you have just measured your watch accuracy and you would like to know if everything is okay. Seems legit! Read along to find out what to do!

Watch accuracy : what is it?

The accuracy of your watch is expressed in seconds per day. If your watch is running at +5 seconds per day (or +5 spd), this means that each day, your watch is gaining 5 seconds. Therefore, each 12 days, your watch will be 1 minute ahead of the « real » time. On the opposite side, if your watch is running at -20 seconds per day, then, your watch will loose 1 minute every three days. Basically, each week; your watch will be 2 minutes and 20 second behind the « real » time. Not so good.

Those numbers look big. Let’s put some perspective. As there are 86 400 seconds composing every single day, loosing or gaining a few seconds each day isn’t that bad in terms of accuracy. For example, -10 spd still represents an accuracy of 99.9884%. Not bad right? However, this little discrepancy, adding up each day may represent quite a gap in the end. We need to find balance.

Watch accuracy : what to aim for?

Obviously, we all want our lovely mechanical watches to be absolutely accurate! The best result would be a nice 0 spd with each measure. While most watchmakers are trying to get closer to that dream, we could consider that any result ranging from -10 spd to +10 spd would be okay if we have a pragmatic approach. Therefore, a really good watch should be somewhere between -5 spd to + 5 spd and an absolute amazing one between -2 spd to +2 spd. This of course depends on the quality of your watch’s movement, if it has been correctly regulated by your watchmaker, if it is brand new or 50 years old and if you are taking good care of it with regular servicing or by following those tips.

Watch accuracy : so what should I do?

First of all, measure the accuracy of your watch regularly. You can use the Toolwatch website or our iPhone and Android app. Then, if you observe a bad result, check what should be expected with your watch. Most watchmakers have a tolerance range for each of their calibers and watches sold should stay in between that range. If you are not sure, contact directly your watchmaker. If your watch is out of that range and still under warranty, then you can ask your watchmaker to regulate your watch to their tolerance for free.

As a lot of factors may disrupt the accuracy of your watch, make sure to check it regularly and to follow our best tips to keep your accuracy at its best!

Watch accuracy : what about the certificates?

The three main one are the COSC (Chronometer) with -4 spd / + 6 spd, the Rolex Superlative Chronometer with -2 spd / +2 spd and the METAS ranging from 0 to +5 spd. While certificates may assess other elements of the watch such as the water resistance or magnetic resistance, all certificates are there to guarantee a certain level of accuracy for mechanical watches.

Buying a watch? Selling a watch?

Want to invest & make money?

Before you do anything, you need to read this helpful guide from Marcelo at Prestige Watches.