Updated May 2023
For new and seasoned watch enthusiasts alike, mastering the myriad of terms specific to timekeeping can seem challenging. However, a basic understanding of various features and functions is invaluable for any watch collector.
In this article, we’ll be discussing tachymeters. You’ll learn what tachymeters are, how to use them, and what types of watches usually have tachymeters. We’ll also cover why you might want to consider adding a tachymeter-equipped watch to your collection of watches.
What is a Tachymeter?
A tachymeter is a specialized watch feature that relies on a scale inscribed around the outside rim of a watch, either as part of the rotating bezel or fixed on the watch case.
A tachymeter can be used to calculate speed based on travel time or to measure distance relative to speed. One of the biggest benefits of using a tachymeter is that its functionality is independent of any unit of distance, so long as you stick to the same unit of length for your calculations. In simpler terms, a tachymeter can be used for calculating miles, kilometers, meters, or other units per hour. It can also measure the frequency of a regularly occurring event in occurrences per hour.
Essentially, a tachymeter is a tool that allows the watch wearer to convert elapsed time (seconds per unit) to speed/rate (units per hour).
What Types of Watches Have Tachymeters?
Tachymeters are primarily found on racing watches, a style well-known for its sleek, attractive appearance and valued role in the world of competitive driving. However, even if you aren’t planning to find yourself on a racetrack anytime soon, you can still find many uses for a racing watch’s tachymeter and chronometer.
In general, chronograph watches will always include a tachymeter, particularly watches produced by luxury brands such as Rolex or Omega.
How to Use Tachymeter Measurements
In order to learn how to use a tachymeter on a watch, there are four key steps you will need to understand.
Step One: Know the Formula
Basic math is an essential component of utilizing a tachymeter.
There are 3,600 seconds in one hour. Therefore, the formula used to calculate speed based on the tachymeter’s reading will be T=3600/t. In this formula, T is the measurement of your tachymeter scale, and t is the time that has passed as displayed on your chronograph.
Using this formula, you are able to calculate the average speed over a specific distance. Elapsed time will be divided by the number of seconds in an hour. Based on these calculations, you can figure out how fast you are traveling by starting your chronograph when you are at your initial “starting line” (Point A) and stopping it at the “finish line” (Point B). When you stop it, the number on the chronograph equates to the number of seconds it took you to get from Point A to Point B. Then, the number displayed on the tachymeter is your speed (in MPH).
Step Two: Does Your Watch Have a Tachymeter?
Not every watch has a tachymeter. Usually, a tachymeter will be clearly labeled on a watch. If it is not, you can check to see if the watch’s bezel rotates. If it does, it is unlikely that it has a tachymeter (though it is possible for a select few models). Usually, a rotating bezel with a numeric complication is a tool other than a tachymeter.
Step Three: Know the Distance Between Two Points
You will also need to know the exact amount of ground you (or the object you are tracking) will cover within the fixed period of time so that you can get an accurate measurement using your tachymeter. Select a Point A and Point B (referenced above), then measure the distance between points.
Step Four: Know How to Read Your Chronometer
If you are using a chronograph watch featuring a tachymeter, you first need to be familiar with how a chronometer works. The chronometer serves as the stopwatch, equipped with a start and stop hand for tracking elapsed time. Chronograph watches have a third hand (in addition to the standard minute and hour hands), which will spin when the chronometer is activated by the wearer.
A chronometer’s numbers measured seconds, but a tachymeter’s units correspond to speed traveled (MPH). So, you’ll need your chronometer in order to read the tachymeter. Familiarize yourself with the chronograph’s stopwatch function, and you will be better equipped to use it for reading the tachymeter. Together, these two watch complications allow you to track speed over a specific distance.
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A watch with a tachymeter can prove helpful in a broad range of applications, even in everyday life when you least expect it. Regardless of the specific features you seek, investing in a high-quality watch is a decision you won’t regret.