Bicycle Gear Ratio Calculator

About this calculator

A bicycle's gear ratio is simply the number of chainring teeth divided by the number of cog teeth — a 50-tooth chainring paired with a 25-tooth cog gives a 2.0 ratio, meaning the rear wheel turns twice per pedal revolution. Multiplying that ratio by the wheel's diameter gives gear inches (a legacy of the old high-wheel penny-farthing, still used to compare gearing across different wheel sizes), and multiplying by the wheel's circumference gives meters of development — the distance traveled per pedal stroke.

This calculator takes chainring, cog, and wheel size and returns all three measures, letting you compare gearing across bikes with different wheel diameters (700c road wheels vs. 26" or 29" mountain wheels) on equal footing. Cyclists, bike fitters, and track/gearing enthusiasts use it to choose chainring/cassette combinations that suit a course's terrain, pick a single-speed or track cog, or compare setups before a component swap.