Cycling Cadence to Speed Calculator
Estimate bike speed from cadence and gearing without needing a power model.
How to use this calculator
- Enter cadence in crank revolutions per minute. Use the cadence you can actually sustain for the scenario rather than a momentary maximum unless that is what you want to model.
- Enter the active chainring and rear-cog tooth counts so the calculator can determine wheel revolutions per crank revolution.
- Enter effective wheel-and-tire diameter. A measured rollout or actual outside diameter is more precise than a nominal wheel label.
- Compare different cogs at the same cadence to see how cassette choices change theoretical speed, or compare different cadences in the same gear to see the speed range of that gear.
- Do not treat the result as a performance prediction. It assumes the rider has enough power to maintain the entered cadence against gradient, wind and rolling resistance.
Formula and assumptions
Wheel RPM = cadence × chainring teeth ÷ rear-cog teeth. Road speed = wheel RPM × wheel circumference after converting distance per minute to the chosen speed units.
GIIRR calculates idealized geometry and kinematics. Friction, slip, compliance, tire deformation, manufacturing tolerances and control-system behavior can move real measurements away from the theoretical result.
Worked example
At 90 rpm cadence with a 50-tooth chainring, 17-tooth cog and 27.5-inch effective wheel, wheel speed is about 264.7 rpm and theoretical road speed is roughly 21.7 mph. Shifting to a 25-tooth rear cog at the same cadence lowers the tooth ratio from 2.94 to 2.00 and theoretical speed to about 14.8 mph, while providing more mechanical leverage.
Frequently asked questions
Does this include coasting?
No. It assumes continuous pedaling at the entered cadence and a direct mechanical relationship through the selected gear.
Why can my bike computer differ?
Actual rolling circumference, sensor calibration, tire deformation and small measurement differences affect the distance recorded per wheel revolution.
Does this say whether I can hold that speed?
No. The calculator contains no power, gradient or aerodynamic model. It only answers what speed corresponds to a given cadence and gearing if the cadence can be maintained.
Can I compare 700c and 29-inch setups?
Yes if you enter realistic effective outside diameters for the actual tires. Nominal labels alone can hide meaningful tire-size differences.
Why does a smaller rear cog increase speed at the same cadence?
A smaller cog raises the chainring-to-cog ratio, so the rear wheel turns more times for every crank revolution.
For safety-critical, legal or fitment decisions, verify the result against manufacturer documentation and physical measurements.
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