Bicycle gearing and speed
Compare gear ratios, development and speed using wheel rollout and pedalling cadence. Drag the graph handles to change inputs and explore the result.
Your inputs
The editable example is illustrative. Enter your own dimensions, operating data, prices, and fees. Results update as you edit.
Calculations run in your browser. Inputs are not saved or sent to analytics.
How it works
- Gear ratio = /; Distance per crank revolution = ×Gear ratio; Speed (km/h) = Distance per crank revolution (m) × (rpm) × 60/1,000
- Worked example: 50/25 = 2; 2.1 m × 2 = 4.2 m; 4.2 × 90 × 60/1,000 = 22.68 km/h
- Supported input limits: : 1 ≤ x ≤ 500; : 1 ≤ x ≤ 500; : 1e-12 ≤ x ≤ 1,000,000,000,000; : 1e-12 ≤ x ≤ 1,000,000,000,000; : 0 ≤ x ≤ 1,000,000,000,000; Optional gear combinations: 0–50
Input and formula key
Your result
Complete the inputs to see your result.
Assumptions and limitations
Measured wheel rollout reflects your tyre better than nominal diameter. Development is distance per crank revolution; speed assumes the entered cadence without wheel slip. The result does not predict sustainable speed, climbing effort or drivetrain losses.
Sources
- NIST — conversion factor conventions Sources reviewed: 2026-10-06
- NIST — conversion factor table B.8 Sources reviewed: 2026-10-06
- OpenStax — circle area and circumference Sources reviewed: 2026-10-06
