Cycling Gear Ratio Calculator
Calculate ratio, gear inches, development and speed at a selected cadence.
What would you like to do next?
Compare a bicycle gear with familiar measures
Enter front chainring teeth, rear sprocket teeth, effective wheel diameter and cadence. The calculator divides front by rear for the drive ratio, multiplies by wheel diameter for gear inches and converts wheel travel per crank revolution into meters of development. Cadence then produces theoretical speed in kilometers and miles per hour.
Use an effective rolling diameter for closer results
Tire size labels and nominal wheel names do not always equal loaded rolling diameter. Pressure, rider load, tire deformation, drivetrain losses, cadence variation and wheel slip affect actual speed. The calculation compares gearing and does not decide whether a ratio is appropriate for terrain, skill or safe bicycle setup.
Frequently asked questions
How is gear ratio calculated?
Front chainring teeth are divided by rear sprocket teeth.
What are gear inches?
They multiply drive ratio by effective wheel diameter in inches.
Is the displayed speed exact?
No. It is theoretical speed at the entered diameter and cadence.