Bike Gear Ratio Calculator
Enter your chainring and cog teeth, wheel diameter, crank length, and cadence to see your gear ratio, gain ratio, and resulting speed.
Speed at Cadence
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Gear Ratio—
Gain Ratio—
Wheel Circumference (m)—
Speed (km/h)—
About this calculator
Calculate your bicycle's gear ratio, gain ratio, and speed at a given cadence based on chainring, cog, wheel size, and crank length.
Frequently Asked Questions
What is gear ratio vs gain ratio?
Gear ratio is simply chainring teeth divided by cog teeth. Gain ratio also factors in wheel size and crank length, giving a more accurate comparison of effort across different bike setups.
Why does crank length matter?
Longer cranks give more leverage per pedal stroke, which changes the effective gain ratio even if the gear ratio stays the same.
How is speed calculated from cadence?
Speed is derived from how far the wheel travels per pedal revolution (gear ratio times wheel circumference) multiplied by your cadence in RPM.