Bike Gear Ratio Calculator
Work out gear ratio, gear inches, and rollout from chainring and cog sizes.
Quick answer: enter your details below and click Calculate Gear — your result appears instantly, right here in your browser. Nothing you enter is uploaded or stored.
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Enter your details below.
How to use
- Enter front chainring teeth.
- Enter rear cog teeth.
- Click Calculate Gear.
About this tool
Enter the front chainring teeth and rear cog teeth. The tool divides them for the ratio, multiplies by a standard 27-inch wheel for gear inches, and converts to metres of travel per crank turn. Bigger numbers mean a harder, faster gear.
Frequently asked questions
What are gear inches?
Gear inches express the gear as the diameter of an equivalent direct-drive wheel, a traditional comparison number.
Is a higher ratio always better?
No. A higher ratio is faster on the flat but harder on climbs; range matters more than any single gear.