A tachymeter scale is a feature found on many watches that allows the user to calculate speed over a known distance. It is typically found on the outer bezel of the watch, and features markings and a numerical scale that corresponds to elapsed time. By timing an event such as a race and counting the number of markers that pass by on the tachymeter scale, the user can determine the speed of whatever event was timed. The tachymeter scale is a useful tool for measuring speed and distance.
