What this calculator does
Bike gear ratio & speed works out gear ratio, development and road speed for a given chainring, cog and cadence. 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
Formularatio = front teeth / rear teeth; development = π × wheel diameter × ratio; speed = development × cadence
The inputs explained
| Field | What to enter |
|---|---|
| Chainring teeth | A number. Starts at 50. |
| Rear cog teeth | A number. Starts at 16. |
| Wheel diameter (mm) | A number, measured in mm. Starts at 700. |
| Cadence (rpm) | A number, measured in rpm. Starts at 90. |
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 chainring teeth
Every other input is held at the calculator’s starting values while chainring teeth varies. Select any row to load that scenario into the calculator.