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 rim numbers make this look like a bigger deal than it is. A 26" mountain rim is 559 mm and a 700c road rim is 622 mm, an 11% gap, so you would expect the mountain bike to be a lot slower at the same cadence. It is not, because you have to measure the whole wheel including the tyre, and the mountain bike is wearing a much fatter one.
A 26 × 2.1" wheel comes out around 667 mm overall. A 700 × 25c is about 672 mm. That is a difference under 1%, well inside the error of your tyre pressure. Put a 29er wheel on instead (738 mm) and the mountain bike is now the taller of the two.
So gearing, not wheel size, is why a road bike is faster at the same cadence. Measure the rolling diameter of what you actually ride rather than trusting the number stamped on the rim.
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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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