Gear Ratio Calculator
Enter your chainring, cog, wheel size, and cadence to see gear ratio, gear inches, development, and speed — and compare gearing across wheel sizes fairly.
Pick the gear before you buy the parts
Choosing a chainring or a cassette is really a question about your lowest climbing gear and your highest descending gear. Seeing those in gear inches and development — instead of raw tooth counts — makes it obvious whether a 30- or 32-tooth ring will spin out or grind on your local trails, and how a wheel-size change shifts the whole range.
When you settle on a chainring and cog, the Chain Length Calculator tells you how many links to run, and the Wheel Size Convertershows how rollout changes between 26″, 27.5″, and 29″.
Frequently Asked Questions
What are gear inches, and why not just use the ratio?
The raw ratio (chainring teeth divided by cog teeth) tells you how many times the wheel turns per pedal stroke, but it ignores wheel size. Gear inches folds the wheel in: it is the diameter of an old direct-drive penny-farthing wheel that would give the same push per stroke. Because it accounts for the wheel, gear inches let you compare a 29er and a 26er fairly — the same 32×50 gear is noticeably taller on the bigger wheel.
What is 'development'?
Development is the distance the bike travels in one full turn of the cranks, in metres. It is gear inches expressed as real ground covered, which many riders find more intuitive than an abstract inch figure. A low climbing gear might roll only two metres per pedal stroke; a big top gear several metres. It is the number that most directly answers 'how far does one pedal stroke take me?'
How is the speed figure worked out?
Speed is development multiplied by your cadence (pedal revolutions per minute) — how far each stroke goes, times how many strokes per minute. It assumes the tire rolls without slipping and ignores wind, gradient, and rolling resistance, so it is a clean comparison between gears rather than a promise of trail speed. Use it to see which gear keeps you in a comfortable cadence at your target pace.
Why does wheel size change my gearing?
A bigger wheel rolls further per turn, so for the same chainring and cog it pushes a taller effective gear. Moving from 26" to 29" raises your gear inches by roughly ten percent, which is why many riders fit a larger cassette cog or a smaller chainring when they go up a wheel size to keep the same climbing gear. The Wheel Size Converter shows that rollout difference directly.
Comparison figures for choosing gearing, not a measured trail speed. Real speed depends on gradient, surface, wind, and rolling resistance.