What this calculator does
Gear Ratio works out output speed and torque of a gear pair from the tooth counts and the input speed. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaGR = Nout/Nin; ωout = ωin/GR; τout = τin×GR
The inputs explained
| Field | What to enter |
|---|---|
| Input (driver) gear teeth | A number. Starts at 12. |
| Output (driven) gear teeth | A number. Starts at 36. |
| Input speed (rpm) | A number, measured in rpm. Starts at 1000. |
| Input torque (N·m) | A number, measured in N·m. Starts at 5. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with input (driver) gear teeth
Every other input is held at the calculator’s starting values while input (driver) gear teeth varies. Select any row to load that scenario into the calculator.
How the answer changes with input (driver) gear teeth