What does tachymeter mean?
A tachymeter is a device or scale for determining speed. Its basic principle is to relate distance to elapsed time: if an observer measures the distance covered during a known interval, the speed can be calculated. Optical tachymeters have historically been used in surveying and aviation, allowing speed to be estimated without requiring the moving object to stop. The word is also familiar in horology because many chronograph watches include a tachymeter scale around the dial. Starting the chronograph and the seconds hand at a marked point allows the wearer to calculate the average speed over a specified distance, commonly one kilometre or one mile. A tachymeter is therefore associated with measurement, precision, and technical expertise. Although some devices may serve related purposes, a tachymeter specifically expresses speed through the relationship between distance and time, while a tachometer more often measures rotational speed.
nounAn instrument or measuring scale used to determine speed, especially by calculating speed from distance covered during a known interval of time. On a chronograph watch, it is a scale that indicates average speed over a prescribed distance.
- An instrument used to measure speed, especially in surveying or other situations where distance and elapsed time are observed.
- A graduated scale or function on a chronograph watch that calculates average speed over a prescribed distance.
"The surveyor used a tachymeter to calculate the train's speed as it passed the observation point."
"Using the optical tachymeter, the engineer estimated the aircraft's speed without slowing it down."
"The watch has a tachymeter scale around its dial for calculating speed."
The plural is used when referring to multiple instruments or separate tachymeter functions or scales.
"The survey team carried two tachymeters for measurements taken at different points."
On a chronograph, the tachymeter turns the sweep of the seconds hand into a speed reading.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does tachymeter come from?
Tachymeter was borrowed into English in the early nineteenth century from French tachymètre. It was formed from Greek takhys, meaning “swift” or “fast,” and metron, meaning “measure,” reflecting the instrument's purpose of measuring speed. Related English words such as tachyon and tachycardia share the same Greek element for speed or rapidity.
Related word forms
How tachymeter is actually used
This is primarily technical vocabulary. Surveyors, engineers, and racing or horology enthusiasts use it, while general audiences may encounter it in connection with chronograph watches.
Easily confused with tachymeter
A tachymeter generally determines speed from distance and time, whereas a tachometer usually measures rotational speed, such as the revolutions per minute of an engine.