What is the difference between a Chronograph and a Chronometer?

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At first impression, you may not find any difference between Chronograph and Chronometer because both have a common word “Chrono” which is related to time and words “graph” and “meter” are related to measurement. But in technically, both Chronograph and Chronometer have their own meaning. In the following paragraphs, you will find the differences between a Chronograph and a Chronometer.

Technically, Chronograph is an additional function/complication of a watch where as Chronometer refers to a certification awarded to a timepiece for its accuracy and reliability.

Generally speaking, Chronograph or Stopwatch is a piece of equipment used to measure and record periods (intervals) of time. In watchmaking, the timepieces with additional Stopwatch function (it can be analogue or electronic) are known as chronograph watches. A chronograph watch features separate counters (sub-dials) to measure the intervals of time and has dedicated buttons or pushers to activate chronograph function.

Chronometer is a wristwatch that carries a certification for its accuracy and precision. A chronometer may be a simple three hands watch or a complication timepiece equipped with additional functions such as calendar, chronograph, tourbillon etc.

The term Chronometer was originated in 18th century and used to indicate high precision mechanical clocks used in ships to assist celestial navigation and determination of longitude. Invented by John Harrison in 1730, the marine chronometers became as essential navigational equipment for sailors until the radio communication and now GPS systems replaced them. Still, mechanical chronometers are being used in many ships as a backup in case of complete failure of the advanced systems.

Gradually, more stringent accuracy tests for marine chronometers came in to existence in order to ensure accurate marine navigation. These tests later adopted in the category of mechanical wristwatches too.

In the past (until 1970s), the chronometric certifications were issued by astronomical observatories such as Neuchâtel Observatory, Geneva Observatory, Besancon Observatory and Kew Observatory in Europe and Japan Chronometer Inspection Institute in Japan.

Today, the Chronometer certificates are issued by independent chronometric institutes. For example, COSC (Contrôle Officiel Suisse des Chronomètres), the Official Swiss Chronometer Testing Institute is responsible for certifying the accuracy and precision of wristwatches in Switzerland. The other two major institutions that undertake chronometric tests of wristwatches in Europe are the Chronometer Observatory Glashütte in Germany and the Besançon Astronomical Observatory (the Observatoire National de Besançon) in France.

The watches that carry certificates from the above institutes are generally termed as Chronometers. According to the Official Swiss Chronometer Testing Institute, only about 6% of all Swiss watches exported have the title of certified chronometer and approximately 21% of the exported mechanical wrist watches are certified chronometers. The most stringent COSC tests are based on the criteria set by the ISO 3159 (2009 Edition). COSC also issues chronometer certification to quartz watches.

Not all manufactures offer certified chronometer timepieces. The timepieces that succeed the stringent tests employed by the respective Chronometer Testing Institutes are only eligible to be labeled as the Official Certified Chronometers. So, next time when you purchase a timepiece with Chronometer label, make sure that the watch really carries certification from any of the Chronometer Testing Institutes.

Following data will give you a rough idea about the number of chronometer watches certified by COSC every year.

COSC Statistics (2015) – Brands and number of Chronometer certified watches

  • ALEXANDRE MEERSON – 18
  • ATLANTIC – 187
  • AUDEMARS PIGUET -17
  • BALCO – 1’901
  • BALL WATCH – 5’031
  • BREITLING – 147’917
  • BREMONT – 5’860
  • BURBERRY – 100
  • CARL. F. BUCHERER – 4’577
  • CENTURY – 200
  • CERTINA – 1’469
  • CHANEL – 154
  • CHOPARD – 16’107
  • CHRISTIAN DIOR – 2
  • CHRISTOPHE CLARET – 52
  • CHRISTOPHER WARD – 3’362
  • CLERC – 441
  • DELMA – 93
  • DOXA – 919
  • ENICAR – 34’468
  • ERNEST BOREL – 2’540
  • ETERNA – 13
  • FERDINAND BERTHOUD – 1
  • GOLAY SPIERER – 8
  • GRAND PRIX – 494
  • INVICTA – 989
  • JUNGHANS – 500
  • LONVILLE – 7
  • LOUIS MOINET – 101
  • LOUIS MONNIER – 13
  • MANJAZ – 1’329
  • MIDO – 49’922
  • MUEHLE-GLASHUETTE – 177
  • OFFICINE PANERAI – 6’262
  • OMEGA – 511’861
  • PALLADIUM – 99
  • PARMIGIANI, FLEURIER – 56
  • RADO – 104
  • RALPH LAUREN – 17
  • RANCEAS – 132
  • ROAMER – 1’444
  • ROLEX – 795’716
  • SCHWARZ ETIENNE – 997
  • SELLITA – 17
  • STEINHART – 99
  • TAG HEUER – 693
  • TAVANNES – 82
  • TISSOT – 96’563
  • TITONI – 4’146
  • TUDOR – 23’003
  • ULYSSE NARDIN – 2’561
  • VACHERON CONSTANTIN – 99
  • VAN GOGH – 9
  • WOSTEP – 24
  • ZENITH – 6’824
  • ZODIAC – 89