Bike Cadence & Speed Calculator
Optimize your cycling gear ratio. Convert RPM to Speed for Road, MTB, and Gravel bikes with precise tire sizing.
About
Cyclists constantly seek the optimal balance between pedal speed (cadence) and gear selection to maximize efficiency. This calculator connects the mechanical variables of your drivetrain to actual road speed. It is essential for triathletes dialing in time trial pacing or mountain bikers selecting a 1x chainring size. The physics is simple but precise: one rotation of the cranks turns the rear wheel a specific number of times based on your gear ratio. The distance traveled depends on the tire circumference. By inputting your specific components, you can prevent "spinning out" on descents or grinding too hard on climbs. Accurate tire circumference values are included for standard Road (700c), MTB (29", 27.5"), and Gravel sizes.
Formulas
Speed is calculated by multiplying the angular velocity of the cranks by the gear ratio and the wheel perimeter.
To convert to Imperial units:
Reference Data
| Tire Size | Circumference (mm) | Gear Ratio (50/11) | Speed @ 90 RPM |
|---|---|---|---|
| 700x23c | 2,096 | 4.55 | 51.5 km/h |
| 700x25c | 2,105 | 4.55 | 51.7 km/h |
| 700x28c | 2,136 | 4.55 | 52.5 km/h |
| 29x2.25" | 2,281 | 3.00 (32/11) | 37.0 km/h |
| 27.5x2.1" | 2,148 | 3.00 (32/11) | 34.8 km/h |
| 650b x 47 | 2,194 | 3.64 (40/11) | 43.1 km/h |