Chronograph vs. Chronometer

Enhancing Your Watch Knowledge

Although the words chronograph and chronometer may sound similar, they’re two totally different concepts in watchmaking. In the simplest terms, a chronograph is a watch complication. In horology, a complication is any feature of a watch that goes beyond basic hours and minutes. Even a date function is a complication, like a chronograph. On the other hand, a chronometer is a term used to describe a particular type of watch. It’s one that’s satisfied very specific criteria for precision. A chronometer is not a complication or additional function of a watch. Now, let’s dive deeper into these two characteristics so you can fully understand each.

What is a Chronograph?

The term chronograph derives from the Greek word for “time recording,”  “khronographos.” Master watchmaker and astronomer Louis Moinet invented the mechanism over 200 years ago in 1816. In the past century, the chronograph has become a relatively common feature on sport models, like racing and yacht watches.

At the most basic level, a chronograph is a stopwatch function for a mechanical timepiece. It’s comprised of an independent sweep seconds hand that’s started, stopped, and returned to zero by pressing on the pushers. The pushers are typically located on the watch case at the two and four-o’clock positions. When you engage the pushers, the time on the watch remains unaffected. Instead, they initiate a sweep seconds hand, which allows you to measure elapsed time.

Although the dial layouts of watches with chronograph functions vary, most models will have chronograph registers. These subdials often display counters in intervals of 30-minutes, twelve-hours, and 60-seconds at the three, six, and nine-o’clock positions respectively. One famous example of a watch with a chronograph function is the TAG Heuer Carrera. However, it’s interesting to note that most Carrera’s have a different layout of the subdials. This is because of the presence of a date complication at the three-o’clock position. Instead, its chronograph registers are commonly located at the twelve, nine, and six-o’clock positions.

 

In addition to the standard chronograph, there are variations on the complication. For example, there’s the monopusher chronograph that operates with only one pusher. There’s also the split-second chronograph. It allows you to measure two intervals that start at the same time but end at different times. Two examples of these iterations are the Montblanc Monopusher Chronograph and the OMEGA Speedmaster Split-Seconds Chronograph.

What is a Chronometer?

Watchmakers first developed the concept of the chronometer to measure the accuracy of timepieces. Time is a very precise measurement. On the other hand, watches are man-made and thus have a certain degree of imperfection.

Today, if a watch is a chronometer or chronometer certified, it has met a specific set of precision standards. The International Organization for Standards (ISO) defines the categories, test program, and minimum requirements for chronometers. The ISO has also accredited certain institutions to test and grant chronometer certification. One of the most common is the Controle Officiel Suisse des Chronometres (COSC).

 

 

In order to obtain chronometer certification, watches must undergo four types of tests. They take place over the course of several days, in five different positions, and at three different temperatures. Next, the watches must go through daily tests for a period of fifteen days and must meet seven criteria. If and only if they meet those seven criteria, the watch gets the esteemed privilege of displaying “chronometer” on its dial.

Some brands have taken the chronometer certification process a step further. They’ve developed their own procedure in addition to the ISO standards. One example is Rolex, who offers watches with a Superlative Chronometer certification. For instance, the ISO standard for accuracy is -4/+6 seconds per day. Rolex’s Superlative Chronometers have accuracy of -2/+2 seconds per day. The Cosmograph Daytona is just one Rolex model that’s Superlative Chronometer certified.

Can a Watch be a Chronograph and a Chronometer?

While a chronograph and chronometer are two completely different entities, they’re not mutually exclusive. A chronograph model may in fact be a chronometer as well. Certain Rolex Daytona and OMEGA Speedmaster models come equipped with both this complication and a chronometer certification.