Fixed Gear Ratio
Calculator.
Work out your fixie or track gearing. Enter chainring, cog, wheel size and cadence to get gear ratio, gear inches, skid patches, development and speed.
Results update as you type. Try changing the cog by one tooth and watch what happens to the skid patch count.
How the calculator works
A fixed gear bike has exactly one gear, so choosing it well matters more than on any other bike. Two numbers decide everything: the teeth on your chainring and the teeth on your cog.
A quick rule for picking gearing: choose your ratio for the terrain first, then nudge the cog by a tooth until the skid patch count is above about 8. You barely change the feel of the gear and you triple the life of your tire.
Fixed gear ratio FAQ
Most city fixed gear riders run between 2.6 and 3.0, which is roughly 70 to 78 gear inches. A 46 x 17 (2.71, about 72 gear inches) is the classic all-round setup. Hilly cities favour something lower like 44 x 17, while flat cities and track riders go higher, often above 3.2.
On a fixed gear you slow down by resisting the pedals, which wears the tire at specific points. The number of distinct wear points is your skid patch count, and it depends on the ratio between chainring and cog teeth. More skid patches spread the wear across the tire, so it lasts much longer.
Reduce your chainring and cog to lowest terms. The reduced cog number is your skid patch count. A 48 x 16 reduces to 3 x 1, so just 1 skid patch, which shreds a tire fast. A 48 x 17 does not reduce, giving 17 patches. If the reduced chainring number is odd, an ambidextrous skidder who can skid with either foot forward doubles the count.
Avoid ratios that reduce to a small number, such as 48 x 16, 44 x 22 or 42 x 14. They give you one or two skid patches, which wears a hole through a rear tire in weeks if you skid to slow down. Shifting the cog by a single tooth usually jumps you from 1 patch to 15 or more.
Gear inches equal your gear ratio multiplied by the wheel diameter in inches. It is the standard way fixed gear and track riders talk about gearing, since it puts every setup on one scale. Track sprinters often run 88 to 108 gear inches, while street riders sit closer to 70.
In most places, yes, and it is a good idea everywhere. Skidding works but stops you far slower than a front brake, and it destroys tires. Many jurisdictions legally require at least a front brake on any bike ridden on the road, fixed gear or not.