Gear Ratio Calculator
Ratio = driven teeth / driver teeth. Optional input RPM gives output RPM as input RPM / ratio. Informational, not a gearbox rating or code approval.
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How to calculate gear ratio
- Enter driver (input) teeth.
- Enter driven (output) teeth.
- Enter input RPM to see output RPM. Output RPM is input RPM divided by the ratio.
- The default 20 to 60 is a 3:1 reduction, 3000 RPM in, 1000 RPM out. Nothing is uploaded.
Simple gear pair
Ratio = t2 / t1
| Driver | Input gear tooth count t1 |
|---|---|
| Driven | Output gear tooth count t2 |
| Ratio | t2 / t1, also shown as 1 : n |
| Reduction | Ratio greater than 1 slows speed and raises ideal torque |
| Output RPM | Input RPM / ratio |
| Efficiency | Ignored. Not a gearbox rating. |
What gear ratio means here
Ratio is driven teeth divided by driver teeth. 60 / 20 is 3, shown as 1 : 3. Output RPM is 3000 / 3 = 1000. A ratio above 1 is a reduction: speed down, ideal torque up.
Driver, driven, and RPM
The driver is the input gear. The driven gear is the output. Meshed teeth share the same pitch, so tooth count sets the speed ratio. Surface speed of a shaft is a different job on the RPM calculator.
How this page computes
Both tooth counts must be greater than 0. Input RPM must be greater than 0 when you type it. The page does not model idlers, compound trains, or belt pulley diameters.
Limits
No module, no strength, no efficiency. Informational, not a gearbox rating or code approval. CZNull does not receive the tooth counts. See the disclaimer.