What Is Master Chronometer Certification? Is It Different From COSC?

In full transparency, being an Amazon Associate we may collect a small commission (at no cost to you!) when you click on some of the links in this post and make a purchase. These funds allow us to maintain the site and continue to write great articles for you.

Are you looking for the meaning of the master chronometer? Do you want to know what is master chronometer certification?

If you have noticed “Master Chronometer” written on a watch’s dial and are wondering about it then you are reading the right article. In this article, I am not only going to tell you what it means but I will also tell you how it is different from chronometer and superlative chronometer.

So keep reading!

Quick Navigation

What Is Master Chronometer?

What Is Master Chronometer

Let us first address the elephant in the room i.e. master chronometer and then will get into details. So what is a master chronometer? And what does it mean?

A master chronometer is a watch that has been tested and certified by METAS (Swiss Federal Institute Of Metrology).

METAS does a total of 8 tests which take around 10 days to complete. And once the watch passes all these tests then it is awarded the master chronometer certification. These 8 tests can be divided into 4 major categories that are as follows:

  1. Precision test
  2. Anti-magnetic resistance test
  3. Durability test
  4. Water-resistance test

Let us now look at all the 8 tests in brief.

1) Magnetic Resistance Of Movement

In this test, the movement of the watch is exposed to a magnetic field of 15000 Gauss and then its deviation in keeping time is measured. This test basically measures the anti-magnetic capability of the watch’s movement.

2) Magnetic Resistance Of The Whole Watch

In this test, the whole watch is exposed to the magnetic field of 15000 Gauss. Then how the watch’s accuracy is getting hampered in the presence of a magnetic field is observed. Therefore you can say that master chronometers are also anti-magnetic watches.

3) Chronometric Performance

This test includes the daily precision tests of the watch and it runs for 2 days. On the first day, the watch is exposed to a magnetic field of 15000 Gauss and then it is turned in 6 different positions. On the second day the same process is repeated but this time the watch is demagnetized. Then the results of both days are compared to see how the timepiece performed under the effect of a magnetic field and without it.

4) Chronometric Precision

In this test, real-world conditions are simulated and the watch is tested for its precision. The timepiece is exposed to different temperatures, positions, and magnetic fields, and then its accuracy is measured in different conditions.

5) Chronometric Precision Deviation In Six Positions

In this test, the watch is placed in six different positions (or angles) and then the deviation in its precision is observed.

6) Precision Deviation At Different Level Of Power Reserve

This test is done to make sure that the low power reserve of the watch does not affect its accuracy. In this test, the watch is tested at different positions at 100% power-reserve, and then it’s tested again at 33% power-reserve. And then the results are compared.

7) Testing Of Power Reserve

In this test, the power reserve of the watch is tested.

8) Water Resistance Test

In this test, the water resistance of the watch is tested against the rating specified by the manufacturer. Not only is the water-resistance property tested but it is also checked if the moisture is forming inside the watch.

How Accurate Is Master Chronometer?

Tudor Watch

These watches are considered to be one of the most accurate watches in the world and if you are looking for numbers then let me tell you.

The watches whose accuracy falls in the range of 0/+5 secs, 0/+6 secs, or 0/+7 secs per day, depending on the size of caliber, are awarded the master chronometer certification.

Master Chronometer Vs COSC

Master Chronometer Vs COSC

COSC certified watches are the watches that are certified by the institute named COSC (Official Swiss Chronometer Testing Institute). These watches’ accuracy lies between -4/+6 secs per day.

On the other hand, master chronometer watches are the watches that are certified by the institute named METAS (Swiss Federal Institute Of Metrology). The accuracy of these watches lies between 0/+5 secs, 0/+6 secs, or 0/+7 secs per day, depending on the size of the caliber.

Therefore master chronometer watches are more precise and accurate than the COSC-certified watches. And one thing to note here is that master chronometer certification is only awarded to a watch if it is already certified by COSC. If the watch is not certified by COSC then it cannot apply for master chronometer certification.

Master Chronometer Vs Superlative Chronometer

Master Chronometer Vs Superlative Chronometer

We have already discussed what master chronometer watches are, right?

So let me tell you what are superlative chronometer watches. Superlative chronometer watches are mainly made by Rolex. Rolex is known to give its own terms to its different watch parts and similar is the case here.

Once the Rolex watches are certified by COSC, Rolex then further tests its watch’s accuracy on its own. And the watches that pass their tests are named superlative chronometers. These watches are believed to have an accuracy of -2/+2 seconds per day.

Which Was World’s First Master Chronometer Watch?

Now that you know what is a master chronometer and what exactly it means, aren’t you wondering about the first watch that managed to pass this certification?

I know you are!

The watch that passed the tests done by METAS and become the world’s first master chronometer watch was Omega Globemaster. Omega raised the bar of accuracy for every watch manufacturer when it first launched this watch in the year 2015. Nowadays, you will find many Omega watches that are certified master chronometers, and this is also one of the reasons why Omega watches are expensive. Other companies have also followed Omega and come out with the watches that have got master chronometer certification.


What Makes A Watch Master Chronometer?

A watch is called a master chronometer if it manages to get the certification from METAS.

What Is The Meaning Of the Master Chronometer?

Master Chronometer means that the watch has passed the 8 rigorous tests done by the METAS.

How Accurate Is Master Chronometer?

A master chronometer watch does not lose more than 0/+5 secs a day.

Is Master Chronometer Different From Chronometer?

Yes, both are different. Chronometers are certified by COSC and master chronometers are certified by METAS.

Are Master Chronometers More Accurate Than Chronometers?

Yes, master chronometers are more accurate than chronometers.

Tom Nielson

Tom's love for watches started when his grandfather gifted him his Rolex watch when he turned 18! Being a teenager it was a big deal for him. Later when he got his first job he bought Fossil Palm Pilot back in 2003 which was a smartwatch. Since then smartwatches have come a long way and so is Tom's love for them. His experience with watches inspired him to start Wearholic and share his knowledge of wearables including watches, smartwatches, smart glasses, & smart clothing.

Leave a Comment