Bike Gear Calculator — Gear Ratio, Development & Gain Ratio
Enter your chainring and cog tooth counts, wheel circumference and crank arm length to see your gear ratio, the distance you travel per pedal revolution, and the gain ratio — a crank-normalised measure of how "hard" your gear is.
teeth
teeth
mm
mm
Distance the bike travels with every complete pedal revolution
- 1
Gear ratio
50 ÷ 17 = 2.941 - 2
Gear development
2.941 × 2,096 ÷ 1 000 = 6.16Distance (m) the bike travels per complete pedal revolution.
How does this calculator work?
Gear ratio = chainring ÷ cog. Gear development (metres per pedal revolution) = ratio × wheel circumference in mm ÷ 1 000. Gain ratio = gear ratio × wheel radius ÷ crank length — all three measure how far you travel per pedal stroke, with gain ratio being the most comparable across different bike setups.
Formula
How this is calculated
The gear ratio is the simplest metric: it is just the number of chainring teeth divided by the number of cog teeth. A 50/17 combination gives a ratio of 2.94, meaning the rear wheel rotates 2.94 times for every single pedal revolution. Multiply this by the wheel circumference (in metres) to get the gear development — the distance the bike covers per full pedal stroke. A 50/17 with a 700×25c wheel (2 096 mm circumference) develops 2.94 × 2.096 ≈ 6.16 m per stroke.
The gain ratio refines development by accounting for the leverage of the crank arm. It is defined as gear development divided by the circumference traced by the pedal (which equals 2π × crank length). Equivalently: gain ratio = gear ratio × wheel radius ÷ crank arm length. This dimensionless number allows fair comparison across bikes with different wheel sizes and crank lengths — a gain ratio of 6 on a 29-inch mountain bike is genuinely comparable to a gain ratio of 6 on a 700c road bike, whereas raw development figures are not.
Typical road-cycling gain ratios run from about 4 (easy climbing) to 8 (fast flats). Track sprinters use ratios above 8. Mountain bikers often run 2–5. The crank arm length is marked on the crank arm itself; 170–175 mm is standard on road bikes, 165–180 mm on mountain bikes.
Frequently asked questions
Gear development is the distance in metres the bike travels for each complete revolution of the cranks. It equals the gear ratio (chainring ÷ cog) multiplied by the wheel circumference. A development of 6 m at 90 RPM gives a speed of 6 × 90 × 60 ÷ 1000 = 32.4 km/h.
Gain ratio divides development by the lever-arm circle of the crank (2π × crank length), giving a dimensionless number that is independent of wheel size and crank length. It lets you compare the "effort" of different gears across bikes with different wheel diameters fairly. Typical road ratios are 4–7.
The smallest chainring combined with the largest rear cog gives the lowest gear ratio, lowest development and lowest gain ratio — making it the easiest gear for climbing. On a modern road bike that is typically a 34/34 or 34/32 combination; on a mountain bike a 30/50 or 28/50 with a wide-range cassette.
Also known as
TG we-Calculate Editorial Team. (2026). Bike Gear Calculator — Gear Ratio, Development & Gain Ratio [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bike-gear-calculator
TG we-Calculate Editorial Team. "Bike Gear Calculator — Gear Ratio, Development & Gain Ratio." TG we-Calculate. 2026. https://we-calculate.com/calculator/bike-gear-calculator.
TG we-Calculate Editorial Team, "Bike Gear Calculator — Gear Ratio, Development & Gain Ratio," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bike-gear-calculator
@misc{wecalculate_bike_gear_calculator, title = {Bike Gear Calculator — Gear Ratio, Development & Gain Ratio}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bike-gear-calculator}}, year = {2026}, note = {TG we-Calculate} }
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