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Glossary

Superlative Chronometer

A plain-language definition of Superlative Chronometer — what it is and why it matters on a Rolex.

Superlative Chronometer is Rolex's accuracy certification. Since 2015 it means the cased-up watch — after its movement passes the independent COSC chronometer test — is tested again by Rolex to within -2/+2 seconds per day, twice the official chronometer standard, and backed by a five-year guarantee.

Two tests, not one

Every Rolex movement is first certified as a chronometer by the COSC, Switzerland's independent testing body, to roughly -4/+6 seconds per day. Rolex then goes further: after casing, it tests the complete watch — movement, case, and all — to its own stricter -2/+2 seconds per day standard. The green seal and 'Superlative Chronometer Officially Certified' on the dial mark that second pass.

The 2015 redefinition also brought a five-year international guarantee, signalling Rolex's confidence in the cased-watch performance rather than just the bare movement.

Superlative Chronometer FAQ

Superlative Chronometer, answered.

What does Superlative Chronometer mean?

It is Rolex's accuracy rating. Since 2015 the cased watch is tested by Rolex to -2/+2 seconds per day — twice the COSC chronometer standard — with a five-year guarantee.

Is a Superlative Chronometer more accurate than a COSC chronometer?

Yes. COSC certifies the bare movement to about -4/+6 seconds per day; Rolex then tests the finished watch to a tighter -2/+2 seconds per day.