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Gear Ratio Calculator
Enter driver and driven teeth or diameters to get the gear ratio, the output speed and the torque multiplier.
Gear ratio calculator
Gear ratio: —
Output speed: —
Torque multiplier: —
Speed change: —
—
How to use the Gear Ratio Calculator
- Choose whether you are entering tooth counts or pitch diameters.
- Enter the driver value, the driven value and the input speed in rpm.
- Read the gear ratio, the output speed and the torque multiplier.
Features
- Ratios from teeth or from pitch diameters
- Output speed at any input rpm
- Torque multiplier and percentage speed change
- Runs locally, no uploads
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Frequently Asked Questions
Common questions about the free online gear ratio calculator.
Divide the driven teeth by the driver teeth. A 36 tooth driven gear with a 12 tooth driver
gives a ratio of 3 to 1.
Gear ratio equals driven teeth divided by driver teeth, and the same rule works when you use
pitch diameters instead.
Output rpm equals input rpm times driver teeth divided by driven teeth, so 1500 rpm becomes
500 rpm with a 3 to 1 ratio.
Torque is multiplied by the same ratio, so a 3 to 1 reduction triples the output torque while
cutting the speed to one third.
Yes. For gears with the same tooth size the ratio of teeth equals the ratio of pitch
diameters, so either measurement works.
Yes. Sprocket teeth and pulley diameters follow the same rule, so the ratio and the speed
change are calculated in the same way.
Yes. If the driven gear has fewer teeth than the driver the ratio is below one, so the output
turns faster than the input.
No. Every result is calculated locally in your browser, so the figures you enter never leave
your device.
Yes. It is free to use with no account and no limit on how many gear trains you check.
Last updated: October 10, 2026