Cadence to Speed Calculator (Cycling)
Calculate bike speed from pedal cadence, gear ratio, and wheel size.
Convert RPM to mph or km/h for any chainring, cog, and tire combination.
Cadence to Speed
Cadence is how fast you spin the cranks, in revolutions per minute (RPM). Combined with gearing and wheel size, cadence determines how fast the bike actually moves.
Formula
Speed = cadence × gear ratio × wheel circumference
In SI units:
- speed (m/min) = RPM × (chainring / cog) × π × wheel diameter (m)
- multiply by 0.06 → km/h
- or by 0.0373 → mph
Worked Example — 50/15 at 90 RPM, 700×25c
- Wheel diameter ≈ 0.678 m → circumference ≈ 2.13 m
- Ratio = 50 / 15 = 3.33
- Speed = 90 × 3.33 × 2.13 = 638 m/min
- = 38.3 km/h ≈ 23.8 mph
Cadence Reference Bands
| Cadence (RPM) | Style |
|---|---|
| 60–75 | Mashing — heavy load on knees |
| 80–90 | Endurance / sportive (most efficient for many) |
| 90–100 | Pro road racer cruise |
| 100–120 | Sprinting, criterium, track |
| 120+ | Pure spin training, fixed-gear |
Why Cadence Matters
For the same bike speed, lower cadence with a bigger gear loads the muscles more (ideal for short bursts but tiring on long rides). Higher cadence with a smaller gear shifts the load to the cardiovascular system — easier on the legs, harder on lungs. Cyclists typically train to hold ~85–95 RPM as their natural endurance cadence.
Effect of Wheel and Tire Size
The same gearing on a 26" mountain bike runs about 9% slower than on a 700c road bike at identical cadence. That is why a fast mountain biker at 100 RPM can be slower than a casual road rider at the same cadence — the wheels are doing different work per revolution.
Power Connection
Power (watts) = torque × angular velocity. At fixed power, halving the cadence doubles the torque your legs deliver — useful for climbing in low gears, but hard on knees long-term. This calculator gives the kinematic speed; aero drag, grade, rolling resistance, and rider physiology determine whether that speed is sustainable.