Free cycling calculator
Bike Gear Calculator
See every gear on your bike: its ratio, how far one turn of the cranks takes you and how fast you go at your cadence. Compare chainrings and cassettes before you change them.
How the calculation works
A gear’s ratio is the chainring’s teeth divided by the cog’s: how many times the rear wheel turns for each turn of the cranks. Development multiplies that ratio by the wheel’s circumference, the distance the bike moves per crank revolution; gear inches multiply it by the wheel’s diameter in inches. Speed is development times cadence.
The wheel’s diameter is its rim size (the ISO bead seat diameter: 622 mm for 700c and 29″, 584 mm for 650b and 27.5″) plus twice the tire width. Measured on the road, a wheel rolls out about 1% less, depending on the tire and its pressure.
Reading the result
Across Europe, riders describe a gear by its development in metres (a 34 × 34 on a 700c wheel is about 2.1 m); gear inches are the English-speaking convention for the same idea. The range compares the hardest gear with the easiest: at 455%, the hardest covers 4.55 times the distance per turn of the cranks.
With two chainrings, many combinations overlap: different ring and cog pairs give almost the same development. Comparing the columns shows where the gaps and the duplicates are.
Sheldon Brown’s gear theory for cyclists