Bicycle Gear Ratio Calculator

The gear ratio is simply the number of chainring teeth divided by the number of rear sprocket teeth. A ratio of 3.0 means the rear wheel turns 3 times for every full pedal revolution. Higher ratios mean harder pedaling and more speed; lower ratios are easier to push and better for climbing.

Gear inches is a traditional measurement of effective driving wheel size, inherited from the penny-farthing era. It equals (chainring ÷ sprocket) × wheel diameter in inches. A higher number in gear inches means a harder, faster gear — a 100-inch gear is a very high road racing gear, while 30 inches is an easy climbing gear.

Meters of development (also called rollout) is the distance your bike travels forward per complete pedal revolution. It equals the gear ratio multiplied by the wheel circumference in meters. At a gear development of 6 m/rev and 90 RPM, you cover 540 meters per minute — about 32.4 km/h.

The Gain Ratio, introduced by Sheldon Brown, is a dimensionless number that compares the distance the bike travels to the distance your foot moves. It accounts for crank arm length, making it a more physically meaningful comparison than gear inches across different crank lengths. A gain ratio above 5 is a high gear; below 2 is very low.

Most road cyclists and coaches recommend a cadence of 80–100 RPM for efficient endurance riding. Competitive sprinters may hit 120–150 RPM in short bursts. Mountain bikers often settle between 70–90 RPM. A higher cadence generally reduces muscle fatigue and knee stress compared to grinding a big gear at low RPM.

A wider tyre has a larger outer diameter, which increases the effective wheel circumference. This means the bike travels slightly farther per pedal revolution than a narrow tyre on the same rim. The difference is small — swapping from a 23 mm to a 28 mm tyre on 700c adds roughly 15 mm to circumference — but this calculator accounts for it accurately.

For steep climbing, cyclists typically want a gear ratio of 1.0–2.0 (e.g. a 34-tooth chainring and a 34-tooth sprocket gives 1:1). On a 700c wheel that yields around 27 gear inches — very manageable on long mountain ascents. Modern 1× drivetrains with wide-range cassettes (11–51t) are designed to provide these low gears without a front derailleur.

Gear ratio is a pure dimensionless number (chainring ÷ sprocket), while gear inches incorporates the actual wheel diameter to give a measure of effective mechanical advantage on the road. Both express 'how hard is this gear' but gear inches is more meaningful when comparing bikes with different wheel sizes, since a 2.94 ratio on a 700c road bike feels very different from 2.94 on a 20-inch BMX.