Bike Gear Ratios: Chainring, Cog, and What They Mean
Gear ratio turns tooth counts into something you can feel: how far one pedal turn takes you. This calculator shows ratio, gear inches, and rollout together.
What is the Bike Gear Ratio Calculator?
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.
How to use it
- Enter front chainring teeth.
- Enter rear cog teeth.
- Click Calculate Gear.
Worked example
A 50-tooth chainring with a 17-tooth cog gives a ratio of about 2.94, about 79.41 gear inches, and about 6.34 metres per crank turn.
What gear is 50 x 17?
A ratio of about 2.94, or 79.41 gear inches, travelling about 6.34 metres per crank turn.
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.