Gear Ratio Calculator
Calculate gear ratio, output RPM, and output torque for a simple two-gear mesh from tooth counts and input speed/torque.
Enter your values
Tooth counts, then input speed and torque.
How this calculator works
For a simple two-gear mesh, the gear ratio is the driven tooth count divided by the driver tooth count:
Output speed and torque follow from the ratio, assuming an ideal mesh with no power loss:
A ratio greater than 1 means the output gear turns slower than the input but delivers more torque — a speed reducer. A ratio less than 1 is a speed increaser, and trades torque for speed.
Reading the result
| Ratio (GR) | Effect |
|---|---|
| > 1 | Speed reduction, torque increase |
| = 1 | 1:1, no change in speed or torque |
| < 1 | Speed increase, torque reduction |
Frequently asked questions
Does this account for gear mesh efficiency?
No — this calculates the ideal, lossless case. Real gear meshes typically run at 96–99% efficiency per stage; apply that factor to the torque result if you need a realistic estimate.
Can I use this for a gear train with more than two gears?
For a compound gear train, calculate the ratio of each mesh stage separately, then multiply the stage ratios together to get the overall ratio.