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Automotive Calculators

Gear Ratio Calculator

Verified formula Updated Jun 2026 Private — runs on your device

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Verified formula Private

Gear ratio (to 1)

4.000

For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.

How to use the Gear Ratio Calculator

The Gear Ratio Calculator works out your gear ratio (to 1) in an instant. Enter driven gear teeth and drive gear teeth and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.

  1. Enter the driven gear teeth.
  2. Enter the drive gear teeth.
  3. Read off your gear ratio (to 1) — the calculator updates automatically, with no button to press.

Formula

The Gear Ratio Calculator uses the formula:

Gear ratio (to 1) = Driven gear teeth ÷ Drive gear teeth

Worked example

For example, with driven gear teeth of 40 and drive gear teeth of 10, the gear ratio (to 1) is 4.000.

Inputs used
Driven gear teeth 40
Drive gear teeth 10
Results
Gear ratio (to 1) 4.000

Results are estimates for educational use, not professional advice.

Key terms explained

Ratio
A comparison of two quantities showing how many times one contains the other.

Frequently asked questions

Divide the number of teeth on the driven gear by the teeth on the drive gear. A 40-tooth driven and 10-tooth drive gear give a 4:1 ratio.

A higher ratio increases torque and reduces output speed. A lower ratio does the opposite, giving more speed and less torque.

The drive (driver) gear is the input that supplies power. The driven gear is the output it turns.

For multiple gear pairs, multiply the individual ratios together to get the overall ratio of the train.

Enter the driven gear teeth. Enter the drive gear teeth. Read off your gear ratio (to 1) — the calculator updates automatically, with no button to press.

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