Gear & Cadence Calculator
Pick your chainring, sprocket, tyre size and pedalling cadence and see the gear ratio, gear inches, metres of development, and the speed that combination actually produces.
Your numbers
Result
How it works
One turn of the cranks turns the rear wheel chainring÷sprocket times. Multiply that ratio by the wheel’s circumference and you get development — how far the bike travels per pedal revolution. Speed is then simple: development × cadence × 60. Gear inches are the older, stranger unit: the diameter of the penny-farthing wheel that would match the gear, which is why climbers talk about wanting a 25-inch gear and sprinters a 130-inch one.
This is why cadence matters as much as gear choice. The same 50×16 gear produces 19.7 km/h at 50 rpm and 39.4 km/h at 100 rpm — the gear did not change, the engine did.
Good practice & limits
- Spin, don’t grind: most riders are most efficient between 80–95 rpm on the flat.
- Check your lowest gear against your steepest local climb before a trip, not during it.
- Small chainring + big sprocket combinations wear fastest at the extremes of the cassette (cross-chaining).