Sports watches have become more refined and useful through the years. A tachymeter bezel is one of a sports watch’s most common features. Used to measure speed through elapsed time, it remains a staple until today.
In this guide, we’ll show you how to read a tachymeter with step-by-step instructions and some helpful tips along the way.
What is a tachymeter bezel?
Rolex Cosmograph Daytona ref. 116519
A tachymeter scale is a type of graduated scale that permits the measurement of the speed at which an object is traveling. The word comes from Greek “tachys” meaning swift and “metron” meaning measure.
While the first chronograph was invented in 1821 by Nicolas Mathieu Rieussec, they weren’t added to a wristwatch until 1913. The chronograph is needed to work with the tachymeter so the addition of a tachymeter to a wristwatch followed shortly thereafter.
TAG Heuer Grand Carrera Black PVD ref. CAV518B
Wristwatches with a tachymeter became incredibly popular with the rise of automobile racing and increased air traffic.
Your tachymeter is used with the chronograph to measure the time it takes you to travel a fixed distance. You’ll note that the bezel has a confusing and potentially overwhelming number of hashes and numbers, but don’t get discouraged. The reading it gives you is easy to get and somewhat intuitive.
How to use a tachymeter
A tachymeter bezel is a circular scale on the dial of a watch that can be used to measure speed or distance.
Omega Speedmaster Moonwatch Sedna Gold
A tachymeter bezel is a great tool for measuring speed. To do this, you’ll need to know how many miles per hour or kilometers per hour your car can go at a given distance.
You’ll need to use the chronograph push button to start your stopwatch if you’re in your car. When you know your car has traveled one mile or one kilometer, you push the chronograph pusher to stop it.
Take note of where the second hand sits on your tachymeter scale. This number references the speed of the car or whatever vehicle you’re using. It’s mathematics. There are 3600 seconds in an hour. If your vehicle takes 60 seconds to finish that mile, then 3600/60= 60. You’re traveling at 60mph. In this case, your second hand would read 90 for you on the tachymeter.
Breitling Premier B09 Chronograph ref. AB0930
The nice thing is that because this is mathematical the type of distance your measuring is controlled by you. Even if you don’t use a full mile, you can still achieve the finished calculation with a little math.
Keep in mind that many tachymeters don’t measure above 60 seconds. The simple reading off the tachymeter scale will only work if you’re going at higher rates of speed. Tracking slower speeds will take a little more math.
Calculating slower speeds
Breitling Navitimer 01 ref. AB0127
For a runner, the slower speeds are a little harder to calculate, or we should say it takes a little longer to calculate. This is where the flexibility of any distance comes in handy.
Pick a distance to track while running, say 500 feet. Using the same process above, you’re going to start your chronometer with the pusher as you start running. Once you cross the 500 feet mark, stop it. Take a reading in seconds. In this case, let’s say it took you 30 seconds to run 500 feet. Your tachymeter is going to tell you an incredible speed of 120mph.
Obviously, this isn’t correct. You know that 500 ft is a little over a 10th of a mile (10.56 to be exact). To calculate your speed, you must divide the number on the tachymeter by 10.56. 120/10.56 = 11.4mph.
Calculating higher speeds
Rolex Cosmograph Daytona ref. 116519
Tachymeters are also popular with vehicles that travel at much higher rates of speed like aircraft. Unless your watch is capable of reading measurements beyond 60 seconds, you’ll have to do some more math.
In this case, you’ll have to change the fixed distance measurement. It’s easy enough to change the 1 mile to 10 miles. Your tachymeter measures the place taking 20 seconds to move your 10 miles fixed distance. That would give you a measurement of 180mph. Multiply this by 10 since you were measuring 10 miles and you have your actual speed of 1800mph.
Omega Speedmaster Dark Side of the Moon
Because it’s mathematics, even though the tachymeter wasn’t designed to specifically measure distance, you can use it that way. This is dependent on traveling at a constant speed, however. It’s an average speed measurement, so to measure distance anywhere near accurately you must be traveling steadily.
If you’re traveling at 60mph, to measure your distance start the chronometer with the pusher. You’ve traveled a mile when the second hand lands on the 60.
Using a Tachymeter Bezel
Now that you know how to use a tachymeter bezel, it’s time to get out there and try it for yourself!
The tachymeter can be used for so many measurements, even rate of production in a factory. Check out our vast selection of chronograph and tachymeter watches at SwissWatchExpo.com and see what you can measure in your life. You never know when it will come in handy.