How to Read Chronograph Scales

What a scale is and why it exists

A chronograph measures elapsed time with its counters; a scale takes that elapsed time and converts it into something else. Think of a scale as a printed shortcut for arithmetic. The chronograph counts seconds, and the ring printed around the edge of the dial or on the bezel turns those seconds into a speed, a distance or a pulse rate. There are three classic scales, and most chronographs carry just one of them, usually a tachymeter.

One point matters throughout: every scale reading is taken from the centre chronograph seconds hand, not the small running seconds. You start the timer, stop it, and read the figure the hand points to.

Tachymeter, speed over a known distance

A tachymeter measures average speed and is by far the most common scale. It is a graduated ring that begins at 60 and runs clockwise towards progressively larger numbers, because a shorter elapsed time means a higher speed.

Worked example: Start the chronograph as you pass a mile marker, then stop it at the next mile marker. Say the hand stops at 40 seconds. The tachymeter figure opposite 40 reads 90. That means you are averaging 90 units per hour, so 90 mph. The rule never changes: the distance must be exactly one unit, and the elapsed time must be under 60 seconds. Working in kilometres, the same method gives you 90 km/h.

This is the scale most everyday chronographs carry. Of the three watches I recommend, the two Seikos sit in this class. The Seiko Chronograph, Blue Dial is a clean quartz chronograph with a tachymeter ring and a dial that reads clearly in daylight: Seiko Chronograph product page. If you want a more polished, metallic look with a touch more jewellery feel, the Seiko Coutura also carries a tachymeter and is worth a look: Seiko Coutura product page. For a first chronograph with large, easy-to-read sub-dials, the Fossil Grant is a relaxed starting point, though it is a clean Roman-numeral chronograph without a printed scale: Fossil Grant product page.

Telemeter, distance to something you can see

A telemeter works out how far away an event is by timing the delay before you hear it. The logic is simple: you see light instantly, but sound travels at roughly 343 metres per second.

Worked example: Start the chronograph the instant you see lightning, and stop it the moment you hear the thunder. If the hand stops at 5 seconds, the telemeter reads about 1.7 kilometres. Artillery and observation officers once relied on this. Today a telemeter scale is rare, mostly found on military-inspired or classic pilot chronographs. None of the three watches above carry a telemeter, which is why I recommend them for the tachymeter and everyday use, not for this.

Pulsometer, heart rate from a few beats

A pulsometer is a scale designed for doctors. It carries a note such as "graduated for 15 pulsations."

Worked example: Start the chronograph and begin counting a patient's pulse; stop it on the 15th beat. The figure the hand points to is the heart rate in beats per minute directly, with no multiplication needed. The pulsometer is a legacy of physicians' chronographs and survives on only a handful of models today. It is not present on any of the three watches above either.

Which watch actually carries which scale

• The tachymeter is the most common, and the scale you are most likely to find on an everyday chronograph.
• The telemeter and the pulsometer are specialist scales, usually seen on military or medical-inspired pieces.
• The surest way to know which scale a watch has is to read the wording around the dial edge: "tachymetre," "telemeter" or "pulsations."

If you want a refresher on the basic operation, see my guide on how to read a chronograph watch. If you are deciding on a model, the best chronograph watches list is a good starting point, and if it is the Seiko side that drew you in, read my best Seiko watches piece.