A tachymeter is a scale used in conjunction with a chronograph to calculate the average speed of a moving object over a known distance of one unit — typically one kilometre or one mile. To use a tachymeter, the wearer starts the chronograph at the beginning of the measured distance and stops it at the end. The chronograph seconds hand points to a number on the tachymeter scale that represents the average speed in units per hour. For example, if the chronograph hand points to 120 when the seconds hand stops, the object was travelling at an average of 120 kilometres per hour over the measured distance. Tachymeter scales are most commonly printed on the outer chapter ring of the dial or engraved on the bezel, and are calibrated for use with the first 60 seconds of chronograph operation.
In replica watches, tachymeter scales appear on two distinct locations depending on the reference: on the dial chapter ring, as seen on Rolex Daytona inspired references, or on a dedicated tachymeter bezel, as seen on certain Breitling and sports chronograph references. The tachymeter is a printed or engraved scale element rather than a mechanical complication — it requires no additional movement module and functions purely as a reading scale used alongside the chronograph hand. In replica versions, the clarity and alignment of the tachymeter scale printing is an important finishing indicator, as the numerals must remain legible and correctly aligned with the chronograph scale to be usable.
In Practice
- Tachymeter scales are calibrated for the first 60 seconds of chronograph operation. The scale reads from approximately 60 (at the 60-second mark, representing 60 units per hour) to 500 or higher at the beginning of the scale near the 12 o'clock position. Objects travelling faster than 60 units per hour will produce a reading before the 60-second mark; objects travelling slower cannot be measured with a standard tachymeter scale.
- On Rolex Daytona inspired replica references, the tachymeter scale is printed on the raised outer chapter ring of the dial — a distinctive design element that frames the three subdials. The quality of this chapter ring — including the sharpness of the tachymeter numerals and the height and finish of the ring itself — is a primary QC checkpoint for replica Daytona references.
- Tachymeter bezels — bezels with the tachymeter scale engraved or printed on the bezel insert rather than on the dial — appear on Breitling and other sports chronograph references. These bezels may be fixed or unidirectional rotating depending on the reference. The scale on a tachymeter bezel should be clearly legible and correctly aligned with the 12 o'clock position.
- The tachymeter scale is distinct from the slide rule bezel found on Breitling Navitimer references, which performs a wider range of aviation calculations using a circular slide rule rather than a simple speed scale. Buyers sometimes confuse the two — the tachymeter is a simpler, single-function scale while the slide rule bezel is a multi-function calculation tool.
- In QC photos, buyers should verify that tachymeter numerals are sharply printed with consistent ink density and correctly aligned relative to the chronograph subdial or bezel position. Smeared, faded, or misaligned tachymeter printing is a finishing defect that should be identified before accepting delivery.
Related Terms
Chronograph · Tachymeter Bezel · Slide Rule Bezel · Pulsometer · Fixed Bezel
Read Next
For a full buyer's guide to replica Rolex Daytona references — including tachymeter chapter ring quality, movement options, and what to check before buying — read: Replica Rolex Daytona Buyer Guide