« Luxury Watches in the Battle for Precision »
It will still be accurate to the second 729 million years from now: the NPL-CsF2 atomic clock in London. Neither quartz watches nor mechanical timepieces can match that level of precision. But which brands should you actually look at to find the most accurate mechanical watches? From Breitling to Zenith, our magazine presents the most accurate automatic movements in the industry and explains why luck also plays a role when you buy.
Rate Deviation: How Precision Is Measured
To determine how accurately a wristwatch runs, its daily deviation from the exact time is measured. If that figure were zero seconds, we could speak of perfect precision, and the timepiece would be a serious rival to the NPL-CsF2 atomic clock. In reality, however, this is never the case: even quartz watches, known for their exceptional accuracy, drift a few seconds a year away from atomic time. The exception is radio-controlled watches, which never build up lasting rate deviations thanks to regular synchronization with international time signal transmitters. In the mechanical world, different standards apply: top-tier watches stay within a window of -2/+2 seconds per day, but even a five-second difference would be a reasonable figure. At the entry level of mechanical watches, a deviation of 20 seconds per day can sometimes be tolerated. Those, of course, are not the most accurate watches in the industry.
Rolex: The Strictest Criteria, from the Datejust 41 to the Submariner
These days, many watch enthusiasts question whether the prices of new Rolex watches are still justified. One thing, however, is beyond debate: the Geneva-based heritage brand's rigorous precision standards. While COSC still lets deviations of -4/+6 seconds per day pass in its testing procedures, watches bearing the five-pointed crown must meet an accuracy of -2/+2 seconds in their latest calibre generation. The Rolex Datejust 41 was one of the first watches to benefit from calibre 3235, currently Rolex's most accurate automatic movement: thanks to a new barrel, the patented Chronergy escapement with Parachrom hairspring, and other technical refinements, this in-house movement is not only extremely precise but also offers a substantial 70-hour power reserve.
Breitling, TAG Heuer and Co.: Many Brands Rely on COSC
Meeting such exacting precision standards requires considerable technical effort and is difficult to achieve, especially in lower price ranges. Many manufacturers, from entry level to upper class, therefore rely on the standardized, internationally recognized testing procedure of COSC, the official Swiss chronometer testing institute. Even Rolex has its watches issued the coveted certificate and applies its own stricter in-house criteria on top. As a result, not all COSC-certified timepieces are equally precise by a long shot; if you are looking for the most accurate watches, Breitling, for example, is a great place to start. Alongside the in-house B01 automatic movement, the B20, developed in cooperation with Tudor and used in the Breitling Superocean Heritage II, also stands out for its accurate rate. Durable and technically well balanced, it is respected throughout the industry, offers 70 hours of autonomy, and passes the COSC requirements with flying colors.
Besides the Breitling Superocean Heritage II, the TAG Heuer Carrera Calibre 36 deserves a special mention: to build in this automatic movement, the Swiss manufacturer drew on the technical know-how of its LVMH sister company Zenith, whose lineup includes the El Primero, one of the most precise and finest movements of all time. The TAG Heuer Carrera Calibre 36 adopts its high frequency of five hertz, which works in favor of a precise rate, and pairs it with a 50-hour power reserve. If you are looking for highly accurate watches at relatively affordable prices, this is the place to look.
Omega: METAS Certification for Maximum Accuracy
Stricter than COSC is the precision testing of the Swiss Federal Institute of Metrology (METAS), which has become widely known mainly through Omega but is in principle open to all brands. To identify the most accurate mechanical watches, METAS, unlike COSC, measures precision in six positions instead of five, tests complete watches rather than bare movements, and places great emphasis on high magnetic resistance of 15,000 gauss. Eight different tests must be passed under the influence of this magnetic field, with the watches not allowed to deviate more than 5 seconds per day from a perfect rate.
A prime example of what METAS movements can do is calibre 8800 in the Omega Planet Ocean 600M: its free-sprung balance with silicon balance spring ensures exceptional durability and precision, while the rhodium-plated finish with Geneva waves in arabesque is a feast for the eyes. The in-house Co-Axial escapement is, of course, also on board. Despite its 600-meter water resistance, the Omega Planet Ocean reveals its precise beauty through a sapphire caseback. A 55-hour power reserve is a respectable figure.
Zenith El Primero: King of Precise Chronograph Movements
No other mechanical brand comes closer to the accuracy of radio-controlled watches than Zenith. While the "regular" El Primero calibres, with their beat rate of five hertz, are already extremely precise, the Defy collection breaks records with the Inventor: this technical masterpiece reaches an incredible 18 hertz (129,600 vibrations per hour) thanks to the patented in-house Zenith Oscillator in calibre 9100, which replaces around 30 components of a standard movement with a single piece. The precision of this Zenith El Primero is in a league of its own: a maximum rate deviation of 0.3 seconds per day sets new benchmarks for mechanical watches.
Variance: Why Precision Comes Down to Luck
A look at the precision standards of COSC, METAS and Co. shows that, for the accuracy of mechanical watches, only a certain range, such as -5/+5 seconds of daily rate deviation, can ever be guaranteed. In plain terms: every watch ticks a little differently, due not only to tiny mechanical differences but also to the smallest variations in regulation. Keep in mind that a day has 86,400 seconds; if two watches differ from each other by five seconds, the consistency of production is still impressive. Whether you as a buyer receive a piece close to the zero-second mark or to the five-second maximum deviation is a matter of luck.
Junghans: The Most Accurate Radio-Controlled Watches for Absolute Precision
Whether Junghans Force or Junghans Spektrum: if you are looking for perfect precision synchronized with atomic time signal transmitters, you should set your sights on the radio-controlled collections of the Black Forest heritage brand. Good or bad luck doesn't come into play here, because modern radio technology achieves the same result in every watch. The Junghans Force, made entirely of ceramic, is particularly modern and minimalist, while the Junghans Spektrum pursues a more traditional aesthetic with Arabic numerals and a two-tone ceramic and stainless steel case.
