By Zencalcy Editorial TeamLast reviewed About us
Gear inches compare gearing across bikes with different wheel sizes by expressing each gear as the diameter of an equivalent direct-drive wheel. Multiply the wheel diameter in inches by the ratio of chainring to cog teeth. The same gear is also shown as metres of development, a metric measure of how far one crank turn moves you.
Convert gearing into gear inches and metres of development.
gear inches = wheel diameter (in) × chainring teeth ÷ cog teeth metres of development = gear inches × pi × 0.0254
Wheel diameters here are typical totals for a mounted tyre, so a wider or narrower tyre changes them. The metres of development line converts gear inches to metres by multiplying by pi and then by 0.0254 to turn inches into metres.
| Symbol | Meaning |
|---|---|
| diameter | Total wheel diameter in inches, including the tyre. |
| chainring | Teeth on the front chainring in use. |
| cog | Teeth on the rear cassette cog in use. |
A 50 tooth chainring with a 16 tooth cog on a 26.5 inch wheel gives 26.5 × 50 ÷ 16 = 82.8 gear inches. That is about 82.8 × pi × 0.0254 = 6.61 metres of development per crank turn.
Gear inches express a gear as the diameter of an imaginary direct drive wheel that would give the same ratio. The figure is the chainring teeth divided by the cog teeth, multiplied by the wheel diameter in inches. A 52 tooth chainring with a 16 tooth cog on a wheel of about 27 inches gives 3.25 times 27, or roughly 88 gear inches.
The unit dates from the penny farthing, where the pedals turned the wheel directly and the wheel diameter was literally the gear. Modern gearing borrowed the idea as a common scale so that bikes with different wheel sizes can be compared on one number.
Higher gear inches mean a harder, faster gear and lower numbers mean easier ones. A road bike typically spans roughly thirty to forty gear inches in the easiest climbing gear and a hundred or more in the hardest, while a single speed or track bike might run a single gear near ninety.
Because gear inches fold in the wheel diameter, they are more comparable across bikes than a bare tooth ratio. Comparing gear inches against your comfortable cadence also shows how far you travel per pedal stroke, which is the practical sense in which one gear is taller or shorter than another.
Continue with the Power to Weight Calculator, Bike Calorie Calculator, or the Bike Frame Size Calculator — or browse more cycling tools and all sports calculators.
They let you compare gears between bikes with different wheel sizes, since the measure folds wheel diameter into the gearing. Two bikes with the same gear inches feel similarly hard to pedal.
Every result is computed locally in your browser from the formulas shown above. Nothing you type is uploaded, logged, or stored, and no account is required.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Content updated: September 2026