Your next luxury watch could be even more accurate – everything we know so far about the new COSC standard

If you're buying a luxury watch and want to ensure its as accurate as possible, you'll want to look out for something called COSC certification. That classification from the Contrôle Officiel Suisse des Chronomètres certifies that a watch movement runs within certain parameters for accuracy.

For many, COSC certification is the gold standard, and is seen as a marker of excellence which can be relied upon. Now, on the 50th anniversary of the ISO 3159 standard, the organisation has announced an evolution to its ways of working.

Dubbed the "Excellence Chronometer" title, this takes everything that the current COSC certification stands for and amplifies it, with a focus on the needs of the modern watch enthusiast. That includes a stricter rate tolerance, magnetic resistance and verification of the power reserve on offer, all tested in conditions which are more similar to real-world wear.

The rate tolerance is arguably what most people associate with the COSC certification, so lets start there. Currently, such devices must fall within a range of -4/+6 seconds per day, meaning a ten second window. That's going to be slashed to six seconds for the new version, though there's no word on what the parameters are.

The introduction of a 200 gauss magnetic resistance rating is perhaps more of interest. It's a real point of note for some watch lovers, with models like the Rolex Milgauss offering elevated levels of protection.

Perhaps most interesting is that the level noted here is over three times higher than the ISO 746 standard, which equates to just 60 gauss. It could mean extra innovation in this area by brands who want to get the higher certification.

Last, but not least, there will also be testing to verify the power reserve figures touted by brands. That should ensure a little more regulation in that realm, which is always nice to have.

The process will start pilot testing from next month, with a wider reveal at Watches & Wonders in April. Then, in October 2026, brands will enter the new process, meaning we should start to see watches with the certification around the turn of the year.