Tachymeter
A tachymeter is a fixed scale around the bezel or dial rim that turns elapsed seconds into speed. You start the chronograph at a marker, stop it after a known distance, and the seconds hand points to the average speed. It needs a chronograph to be used.
At a glance
- Scale type
- Fixed, chronograph dependent
- Location
- Bezel or dial rim
- Measures
- Average speed over a known distance
A tachymeter is not a new mechanism, it is a fixed lookup scale. The numbers engraved on it pre-solve a division: each elapsed-seconds position already shows how many units per hour that time represents, so you never do the math in your head.
How you read it
Using it comes down to three steps, all built on one known distance:
- Start: trigger the chronograph as you pass a reference point
- Stop: stop it after exactly one mile or one kilometer
- Read: the number the seconds hand sits on is the average speed over that distance
This is why a tachymeter is useless without a chronograph: the scale only converts a running seconds hand into a figure.
Where you find it
It is usually printed on a fixed bezel or around the inner edge of the dial. Among the timing-focused complications, it carries the strongest racing and driving association.
For everyday chronographs that wear this scale, see our guide to the best Seiko watches.
Examples
A quartz chronograph such as the Seiko SSB427P1 pairs its pusher-driven seconds hand with a tachymeter scale, so you can read speed directly over a known distance.
View this watch
Comparison
Tachymeter and telemeter scales read different things from the same seconds hand.
| Option A | Option B | Notes |
|---|---|---|
| Tachymeter scale | Telemeter scale | A tachymeter reads speed over a known distance; a telemeter reads distance from a sound delay, such as lightning to thunder. Both rely on the chronograph. |
Related terms
Watches that show this
Frequently asked questions
Do you need a chronograph to use a tachymeter?
Yes, a tachymeter only converts a running seconds hand into speed, it measures nothing on its own. You start and stop the chronograph over a known distance, then read the value the seconds hand points to on the scale.
What unit of speed does a tachymeter show?
A tachymeter shows speed per hour in whatever distance unit you choose. Measure a mile and you read miles per hour; measure a kilometer and you read kilometers per hour. The scale is the same, your chosen distance sets the unit.