What is a Tachymeter Watch?

Despite being embedded into the bezel of one of the most sought-after Rolex models and the most iconic Omega in history, the Tachymeter bezel is one of the least understood watch features. What the Rolex Daytona and the Omega Speedmaster have in common is a series of descending numbers progressing clockwise around the bezel. Let’s dive into what these numbers mean, and how they are used in conjunction with the chronograph.

Rolex Cosmograph Daytona ref. 116500LN on a Black Everest Rubber Strap

USING A TACHYMETER

The clue to the flexibility of the Tachymeter is right on the bezel: units per hour. What this means is that if you can time it in less than a minute, the watch can tell you how many of those you can do in an hour.

Let’s work with an example: The North Pole Rolex Boutique. Santa’s elves are hard at work assembling movements and performing final QC on a batch of Ceramic Daytonas. Santa, meanwhile, stands by measuring productivity on his own Daytona sporting a black Everest Racing Strap. As an elf begins final assembly on a Rolex, Santa presses the top pusher and starts the timer.  When the lead elf watchmaker hurriedly finishes, Santa stops the chronograph to see that 54 seconds have elapsed. Looking out onto the bezel below, we see that our hand landed right on 67. Santa instantly knows that this elf can produce 67 watches per hour!  (Unfortunately for the author, he is 68th on the list)

USES OF A TACHYMETER

The most obvious use of this bezel feature in motorsports is timing around a fixed course. Should a race car lap a one mile circuit, timing that one lap will give an estimate of the average miles per hour achieved on that track by looking at the same Tachymeter bezel.

The biggest limitation one will find in practical application is that the task at hand cannot take more than 60 seconds. Beyond that and your bezel scale just starts back at the beginning.

WHY IS A TACHYMETER ON A DAYTONA?

Though the primary selling point for a Tachymeter on a Rolex Daytona is to time speed while racing, that’s actually not why it is on there. The biggest clue to the real reason is in the full name of the Rolex Cosmograph Daytona.  During the onset of the space race to the moon, several brands were contending to be the official moonwatch. For its part, Rolex revived a previously-used name Cosmograph, alluding to its lofty goal to fly among the cosmos. The Tachymeter scale was meant to be a feature supplementing the chronograph for NASA use.  

The honor of the moonwatch was not to be, unfortunately, and ultimately another Tachymeter chronograph was selected: the Omega Speedmaster Professional. With that twist of fate and Rolex’s continued focus on motorsports, the Cosmograph instead became the unofficial watch of motorsports.

So while of questionable daily use to the average watch owner, the Tachymeter scale contributes both a classic design element as well as a functional nod to the original purpose of several sports chronographs: to push the limits of human achievement.