A tachymeter is a feature found on many chronograph watches that allows the wearer to measure speed or distance. It consists of a rotating bezel or scale around the face of the watch that is calibrated in units per hour, such as kilometers per hour or feet per minute. The tachymeter is used in conjunction with the chronograph, which can be used to measure elapsed time. By timing a known distance, the wearer can use the tachymeter to quickly and accurately determine the average speed of a vehicle or other object.
