Tachymeter Explained : How Tachymeter Watches Work

Tachymeter watches are some of the most popular items on sales and worn around the world, but most don’t understand what it does and that it is actually not just a word or a gimmick.

A tachymeter scale is usually inscribed around the rim of an analog watch. It can be used to compute a speed based on travel time or measure distance based on speed. The spacings between the marks on the tachymeter dial are therefore proportional to 1/t where t is the elapsed time.

The function performed by a tachymeter is independent of the unit of distance (e.g. statute miles, nautical miles, kilometres, metres etc.) as long as the same unit of length is used for all calculations. It can also be used to measure an industrial production process in units per hour. A tachymeter is simply a means of converting elapsed time in seconds per unit to units per hour.

– Wikipedia

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