How to use the cycling speed from cadence calculator
- Enter your cadence in pedal revolutions per minute.
- Enter the chainring teeth at the front and the rear cog teeth.
- Choose how you give the wheel size, as a rollout in millimeters or a diameter in inches, and enter it.
- Read the speed in km/h and mph, the gear ratio and the distance for each pedal turn. The table shows other cadences.
Formula
Gear ratio = chainring teeth / rear cog teeth
Distance per pedal turn = gear ratio x wheel rollout
Speed (km/h) = cadence x distance per turn x 60 / 1,000. Speed (mph) = km/h / 1.609344
If you give a diameter, the rollout is pi x diameter x 25.4 mm. Rollout means how far the bike moves in one full wheel turn.
90 rpm in a 50 by 20 gear
The ratio is 50 / 20 = 2.5. With a wheel rollout of 2,100 mm (2.1 m) each pedal turn moves the bike 2.5 x 2.1 = 5.25 m. At 90 rpm that is 90 x 5.25 = 472.5 m per minute.
Multiplying by 60 and dividing by 1,000 gives 28.35 km/h, shown as 28.4 km/h, and dividing by 1.609344 gives 17.6 mph. The same gear at 100 rpm gives 31.5 km/h.
Measuring the wheel
The wheel rollout is more exact than a diameter. To measure it, mark the tire at the ground, roll the bike forward one full turn of the wheel with your weight on it and measure the distance. Tire size, pressure and rider weight all change it a little. The 2,100 mm shown is only a starting value to replace with your own measurement.
If you only know the wheel diameter, choose the inch option. The tool multiplies it by pi, which gives the distance around the outside of the tire, and that is a little more than the rollout under load, so measured rollout is better.
What the number means
This is the speed that your gearing and cadence give if the bike rolls without wheel slip. It does not model wind, hills, drivetrain losses or a rider who is coasting. It is useful for comparing gears, working out what cadence you need to hold a target speed, or seeing how a different cog changes your top speed.
The table at the bottom lists the same gear at several cadences. This page is arithmetic only and is not training advice. Related tools include the gear ratio calculator for cars, the bike frame size calculator, the pace calculator and the speedometer error calculator.
Assumptions and limits
- Teeth counts are whole numbers and the wheel measurement is yours.
- There is no slip between the wheel and the road.
- 1 mile is 1.609344 kilometers.
- Wind, hills and drivetrain losses are not modeled.
Frequently asked questions
How do you calculate bike speed from cadence?
Multiply the gear ratio by the wheel rollout to get the distance per pedal turn, multiply by cadence for meters per minute, then by 60 / 1,000 for km/h.
What is wheel rollout?
It is the distance the bike moves in one full turn of the wheel. Measure it by rolling the bike one wheel turn while you sit on it.
How do I convert km/h to mph?
Divide by 1.609344. The calculator shows both so you do not need to.
Why does a bigger cog lower my speed?
A larger rear cog makes the ratio smaller, so each pedal turn moves the bike less far. At the same cadence the speed goes down.