What Is a Tachymeter on a Watch?
A tachymeter on a watch is used to measure speed over an elapsed period of time. It can also be used to compute other things as it is independent from the unit of distance, so you can use it to measure metres, kilometres, miles, nautical miles, and so on.
The algebraic formula used to create a tachymeter is T = 3600 / t. The large T represents the scale, t is how long it takes to complete in seconds, and the 3600 is the amount of seconds in one hour. Most tachymeter scales only work for times starting around 7 seconds and up to 60 seconds, but you can still work out calculations above 60 seconds - it just requires a little bit more mental maths (or our good friend, the calculator).
You should be able to find the tachymeter engraved on the bezel of the watch or the inside track of the dial. Keep in mind that not all watches will have a tachymeter, but it is more common on a chronograph watch.
This might all sound quite complicated, but the tachymeter is quite simple to use once you've got used to it.
How to Use a Tachymeter
To use a tachymeter, you time the event over a measured distance and the result can be read off the scale -- indicated by the chronograph hand and outer bezel.
For example, if you want to time the average speed of a car around a race track and you know the distance between two significant points is one mile, you just press the button at point one to start the chronograph, and again at point two to stop it. When you look at your watch, the time will line up with the mark on the tachymeter, giving you the average speed in m/ph.
Remember that the tachymeter can only measure speeds of 60 units (miles per hour or kilometres per hour) or over. If you want to measure something much slower, like a runner, you need to make some other calculations. For example, if your runner travels 100 metres in 10 seconds, your tachymeter will read that their sprint was an impossible 90 kilometres in an hour. So, in this instance to calculate the real speed, you need to know that 100 metres is 1/10th of a kilometre. You can then divide the 90 kilometres by 10 (since the runner travelled 1/10th of the kilometre), and there you'll have the average runner's speed - 9 km/ph.
You can also measure distance travelled. To do this, you first need to know your travelling speed -- which needs to remain constant. If you're travelling at 60mph, you need to start your chronograph second hand and, once the second hand reaches 60mph, it means you have travelled one mile.
This makes it a great tool for athletes, racers and pilots, but a tachymeter is for anyone -- even just because it adds a bit of a futuristic, fashionable touch to your luxurious timepiece.
Top Watches with a Tachymeter
Want to get your hands - or wrist - on a watch with a tachymeter? Look no further: these are our top picks for stylish timepieces that come with a tachymeter.
The OMEGA Speedmaster is one of OMEGA’s most iconic timepieces. Having been a part of all six lunar missions, the legendary Speedmaster is an impressive representation of the brand’s adventurous pioneering spirit.
This OMEGA Speedmaster Professional “Moonwatch” features a black dial covered by a hesalite crystal and graced by a small seconds sub-dial, 30-minute recorder and 12-hour recorder along with a central chronograph hand. The black bezel, with its tachymetric scale, is mounted on a 42mm stainless steel case and presented on a matching bracelet.
A bold and modern automatic chronograph that evokes the cutting edge spirit of its namesake racing discipline. This Formula 1 watch from TAG Heuer is rich with features and technical detail.
The watch features a black metal casing that houses a precision Calibre 16 automatic movement, while the three chronograph sub-dials and date readout are decked out in contrasting colours for high legibility. The luminescent hands and indexes also make the watch eminently usable in low light conditions.
Written by Holly, for WatchObsession.