GlenCalc

Bike gear calculator

Wheel circumference depends on tire size; 2,105 mm is typical for a 700 × 25c road tire.

Your answer

Gear inches77.6 in
Speed20.8 mph
Development (distance per crank turn)6.19 m
Speed33.4 km/h
Ratio2.94

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How we worked it out

Updated as you change the numbers.

  1. Gear inches = (chainring ÷ cog) × wheel diameter. Speed = development × cadence × 60.

Method and assumptions

Gear inches compare gears across bikes with different wheels. Lower gears (40–50 in) climb; higher (90–110 in) are for speed.

Questions

How fast is 50 × 17 at 90 RPM?

About 20.8 mph (33.4 km/h) on a 700 × 25c wheel.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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