Bike Gear Inches Calculator
Enter your chainring teeth, cog teeth and wheel diameter to get gear inches, the drivetrain ratio and metres of development per pedal turn.
How to calculate gear inches
- Enter the chainring (front) tooth count.
- Enter the cog (rear) tooth count.
- Set your wheel diameter in inches, then read gear inches and development.
Examples
50x15 on a 700c wheel
chainring 50T, cog 15T, wheel 27 in
ratio 3.33, 90 gear inches, 7.18 m development
Hard sprint gear 53x12
chainring 53T, cog 12T, wheel 27 in
ratio 4.42, 119.25 gear inches
Frequently asked questions
What are gear inches?
Gear inches express how far a bike rolls relative to one pedal turn, scaled to an equivalent direct-drive wheel. Multiply the gear ratio by the wheel diameter in inches.
What is metres of development?
Metres of development is the distance the bike travels for one full crank revolution. It equals gear inches times pi, converted from inches to metres.
What wheel diameter should I use?
Use the rolling diameter of the mounted tire in inches. A 700c road wheel is close to 27 inches, which is the default here, while a 26 inch mountain wheel is smaller.
How do gear inches help compare bikes?
Gear inches normalise different chainring, cog and wheel combinations to one number, so you can compare a road bike, a track bike and a fixie on equal footing.
Higher or lower gear inches for climbing?
Lower gear inches make pedalling easier and suit climbing, while higher gear inches push more distance per turn and suit flat sprints and descents.
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