How to Use a Tachymeter on a Dive Watch: Complete Beginner's Guide

What Is a Tachymeter? (Quick Definition)

A tachymeter is a printed scale on a watch that turns elapsed time into a rate per hour — perfect for measuring speed, pace, or production output.

Key Features at a Glance:

• 📍 Printed around the bezel or outer dial
• ⏱️ Works together with a chronograph stopwatch
• ⚡ Designed for measurements within 60 seconds
• 🎯 Most accurate range: 7 to 60 seconds
• 🔧 Found on chronographs and many tool-style dive watches

The Tachymeter Formula (Super Simple)

Here's the only formula you need to remember:

Why 3600?

• There are 3,600 seconds in one hour
• ⬆️ Faster time → higher tachymeter number
• ⬇️ Slower time → lower tachymeter number

How to Measure Speed With a Tachymeter

This is the most common use — measuring how fast something is moving over a known distance.

Step-by-Step Instructions:

• Step 1: Start the chronograph when the car (or object) passes Point A
• Step 2: Stop the chronograph after it travels exactly 1 kilometer or 1 mile
• Step 3: Read the number on the tachymeter scale where the seconds hand stops

Using a Tachymeter for Sports & Running

You don't always need a full kilometer. With a quick math trick, you can measure speed over shorter distances.

Measuring Production Rate & Output

Factories, workshops, and even hobbyists can use a tachymeter to calculate output per hour.

Production Examples:

• 🏭 If a factory finishes one car every 45 seconds → tachymeter shows 80 cars per hour
• ⌚ If one watch takes 100 seconds to assemble → measure half a watch in 50 seconds
• 📊 At 50 seconds, tachymeter reads 72 → that's 72 half-watches per hour = 36 full watches per hour

Tachymeter Quick Reference Table

Final Thoughts