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Watch 101: The Chronometer vs The Chronograph

Did you know that watches—no matter how well-made—lose time each day?

Is a watch by any other name still a watch? Not exactly. 

Take the chronometer and the chronograph. Both are watches, and a chronometer can be a chronograph, and vice versa—but they aren’t quite the same thing. 

The Omega Seamaster James Bond Limited Edition is an example of a chronometer. Photo: Omega

A chronometer is a timepiece that can keep time with great precision. Did you know that watches—no matter how well-made—lose time each day? But the ones that are certified chronometers are able to keep that loss to +/-1 seconds; and at most +6/-4 seconds a day. An independent organization in Switzerland, the Contrôle Officiel Suisse des Chronomètres (COSC), subjects watch movements to a battery of tests, and only those that pass the stringent criteria are issued a chronometer certificate. Other brands, such as Rolex and Patek Philippe, have their own tests and certifications. There are other non-Swiss certifying bodies, but in the world of luxury Swiss watches, the COSC is the way to go.

The Breitling Superocean 42mm, a COSC-certified chronometer. Photo: Breitling.

Now the chronograph, technically, is not a watch, but an added function of a watch. Watches with this function, however, are also called chronographs. Chronographs measure segments of time over a specific period. In layman’s terms? It’s a stopwatch.  You can use it to time everything from how many seconds the green light is on at an intersection to how many hours it takes to shop at the three-day sale at the mall.

The Rolex Cosmograph Daytona is both a chronometer and a chronograph. Photo: Rolex

You can usually tell a chronograph by the subdials: there are usually two to three subdials on the main dial, each with a hand that measures the seconds, minutes, and hours (or in the case of two subdials, the second hand on the main dial can also start and stop at will, measuring out the seconds). The hands on these subdials can be started and stopped at the push of a button. There also are advanced chronograph features, such as the flyback hand (the chronograph hand instantly ‘flies back’ to zero and starts again when you push a button) or a split-second hand (an additional hand that that can stop at a certain point while the other chronograph hand continues with its timing task).

The Montblanc 1858 Split Second Chronograph. Photo: Montblanc

There are many chronographs out there, but not too many of those are certified chronometers. There are not too many certified chronometers, period, chronograph or not. But don’t let that stop you from enjoying your watch.