Saudi Luxury / Watch basics
How to use a chronograph and read a tachymeter
Learn which pusher does what, how to avoid harming the mechanism, and how to turn a timed kilometre into a speed.
A chronograph is a stopwatch built into a watch. On most, the pusher above the crown starts and stops it, and the one below resets it to zero. The tachymeter scale around the dial turns a timed interval into a rate per hour, most often a speed over one kilometre.
Working the pushers and reading the subdials
Press the top pusher and the large central seconds hand starts running, while small subdials count the elapsed minutes, often up to 30, and, on many models, hours. The watch’s ordinary running seconds usually sit in a separate subdial, which is why a chronograph dial looks busy. Not every subdial is a counter: some show a 24-hour indicator or the date, so check the manual before reading one.
Four habits avoid trouble:
- Stop before you reset. A standard chronograph is not designed to reset while running; only a flyback chronograph resets and restarts in one press.
- Leave the pushers alone in water unless the maker says otherwise, because they are openings in the case.
- Check that every hand returns exactly to zero after a reset. If one does not, a quartz model may need its hands realigned, which the manual often explains, and a mechanical one needs a watchmaker.
- Stop it when you have finished timing. A running chronograph uses extra energy, shortening a mechanical watch’s power reserve and a quartz watch’s battery life. Some movements are built to run it all day; the manual says whether yours is.
Quartz or mechanical
A quartz chronograph costs far less, keeps better time and needs only a battery. On many, the stopwatch hand moves in one-second steps. A mechanical chronograph sweeps smoothly, times to a fraction of a second and is the more satisfying mechanism, but it costs more to buy and its full service costs more than a simple watch’s, because there are more parts. Our servicing guide explains what a service involves.
Reading the tachymeter
Start the chronograph as you pass one kilometre marker and stop it at the next. The number on the scale beside the seconds hand is your average speed in kilometres per hour: 20 seconds reads 180, 30 seconds reads 120 and 45 seconds reads 80. The scale is simply 3,600 divided by the seconds taken.
Most scales end at 60, because a kilometre that takes longer than a minute runs off the end. For slower speeds, time half a kilometre and halve the reading. If you are in a car, let a passenger do the timing.
Two other scales turn up on some dials. A telemeter gives distance from the speed of sound: start at a lightning flash, stop at the thunder and read the distance. A pulsometer gives heart rate: start, count the number of beats printed on the scale, stop and read beats per minute.
Choosing one
A tachymeter bezel is easy to read but usually takes the place of a rotating dive bezel. The Seiko SSB385P1 is an inexpensive way to try the format, with 100-metre water resistance. The Seiko Prospex SSC813 adds solar charging and a sapphire crystal. At the luxury end, the Omega Speedmaster Moonwatch 310.30.42.50.01.001 pairs the classic tachymeter bezel with Omega’s calibre 3861. The MoonSwatch versions listed on the site are quartz watches made by Swatch, not Omega Speedmasters, though they share the layout.
For a longer look at one chronograph, read our TAG Heuer Carrera chronograph review. The tachymeter’s maths and its odd cases get full treatment in the arithmetic behind the tachymeter scale.