Cycling Speed Calculator

The gear ratio is chainring teeth divided by cog teeth. Cadence times that ratio gives wheel revolutions per minute, which times the wheel circumference gives distance per minute. Dividing by 60 converts to metres per second, then the tool scales that to km/h and to mph.

Use the rollout of your mounted tire in metres. The default 2.105 m is a good value for a 700x25c road tire. A 700x28c is closer to 2.136 m, a 700x23c near 2.096 m, and a 26 inch mountain tire is roughly 2.07 m, so adjust the field to match your setup.

No. It is a pure drivetrain calculation of theoretical speed from cadence and gearing. It ignores wind resistance, gradient, rolling resistance, drafting and chain friction, so real speed on the road is usually lower for the same cadence.

Many road riders sit between 80 and 100 rpm. A lower cadence pushes a bigger gear with more force per stroke, while a higher cadence spins a smaller gear more quickly. Enter whatever cadence you actually hold to see the matching speed.

Metric regions track km/h while riders in the US and UK often think in mph. The calculator shows both at once so you can compare a target with any bike computer or training app without a separate conversion.

It is chainring teeth divided by cog teeth. A 50 tooth chainring with a 15 tooth cog is 50 divided by 15, which is 3.33. Every full pedal turn spins the rear wheel 3.33 times in that gear.

Every field must be a positive number. If any of cadence, chainring, cog or circumference is empty, zero or negative, the tool shows a short warning instead of a speed rather than returning a misleading value.

Speed and the gear ratio are shown to two decimal places. The underlying maths uses full precision and only the display is rounded, so the km/h and mph figures stay consistent with each other.

No. The calculation runs entirely in your browser, so your cadence and gearing numbers never leave your device and the tool keeps working offline once the page has loaded.