Bike Gear Ratio Calculator
Enter chainring teeth, cog teeth, and wheel size to get the gear ratio, gear inches, and development, plus an estimated speed from cadence. Great for road, mountain, and gravel riders tuning their drivetrain.
Frequently asked questions
What is gear ratio?
Gear ratio = chainring teeth ÷ cog teeth. A higher ratio is "harder" (faster but more effort); a lower ratio is "easier" (better for climbing). It is the most direct measure of drivetrain gearing.
What are gear inches?
Gear inches = ratio × wheel diameter (inches), a traditional unit for gearing feel. About 50 gear-inches is moderate; higher favors speed, lower favors climbs.
What is development?
Development = ratio × wheel circumference, the meters the bike travels per full crank revolution. It is the international standard and is more intuitive (the unit is simply meters).
How do I estimate speed from cadence?
Speed (km/h) = development (m) × cadence (rpm) × 60 ÷ 1000. For example, development 6.9 m at 90 rpm gives about 37.3 km/h.