Work out bike gear ratio development instantly with clear inputs, formula shown and shareable results.
Development is the distance travelled per pedal revolution: gear ratio times wheel circumference. A 50/14 with a 0.67 m wheel gives a 3.57 ratio and 7.52 m per turn, so 90 rpm produces 40.6 km/h. Gear inches, the older measure, expresses the same thing as the diameter of an equivalent direct-drive wheel.
Gear ratio
ratio = chainring teeth / sprocket teeth
Development
development = ratio x pi x wheel diameter
This is an estimate from population-average equations, not a medical or diagnostic assessment. Individual results vary with genetics, training history and technique. Seek advice from a qualified coach or clinician before making significant changes to training.
It survives from penny-farthing days, when the gear literally was the front wheel diameter. It remains handy for comparing setups across wheel sizes.
Around 2.5-4 m per revolution, so that a steep gradient can be ridden at 70-90 rpm rather than grinding at 50.