CogSmith — Single-Speed Calculator

Bike & gearing

Units i

Switch measurements without changing the bike setup.

Chainringsi

Select chainrings

Select any tooth counts from 20T to 60T.

Rear cogsi

Select rear cogs

Select any tooth counts from 7T to 52T.

Wheel diameter (mm)i Chainstay length (mm)i Dropout travel ± (mm)i Target gear inchesi Gear-inch tolerance ±i

Include half-link chainsi

What are gear inches?

Gear inches are a universal way to compare how "hard" or "easy" a bicycle gear feels, regardless of wheel size.

Higher numbers (e.g. 75"): A harder gear that travels further with each pedal stroke. Great for flat roads and speed.
Lower numbers (e.g. 50"): An easier gear that requires less effort. Better for climbing hills or trail riding.

The basic calculation is: wheel diameter × chainring teeth ÷ rear cog teeth

Note: Gear inches only describe the ratio, not the physical fit. CogSmith takes this a step further by checking your chainstay length to find combinations that will actually fit your bike without a chain tensioner.

Best combination

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Goldilocks combinations

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perfect frame fit & ideal gearing

Axle adjustment

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shift from current axle position

Chain length

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total length of the chain

Magic gear map

Target gear-inch range Dropout adjustment range Goldilocks combination

Best combinations

Setup	Status	Gear inches	Chainstay	Axle shift	Chain

Mobile app Keep CogSmith in your toolbox Install it on your home screen for quick access at the bike stand or parts bin.