Travel & transport
Cycling gearing calculator
Relate chainring, sprocket, wheel rollout and cadence to geometric speed.
A clear answer. Here’s how.
Gear ratio=front teeth/rear teeth. Distance per crank turn=wheel circumference×ratio; speed multiplies that rollout by cadence. Gear inches use circumference/π as wheel diameter. Assumes direct chain drive without slip or internal hub gearing; tyre loading, drag, gradient and achievable rider power are not predicted.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Front chainring teeth
- 50
- Rear sprocket teeth
- 18
- Measured wheel rollout (mm)
- 2100
- Cadence (pedal revolutions per minute)
- 80
Example result
- Drive ratio
- 2.77777777778
- Distance per pedal revolution (m)
- 5.83333333333
- Geometric speed (km/h)
- 28
- Geometric speed (mph)
- 17.3983933826
- Gear inches
- 73.1026641498