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Gear Ratio Calculator — Chainring to Sprocket Ratio
Calculate gear ratios from chainring and sprocket tooth counts.
How We Calculate This
Gear Ratio Formulas
- Gear Ratio = Chainring teeth ÷ Sprocket teeth
- Gear Inches = Gear Ratio × Wheel diameter (inches)
- Development (m) = Gear Ratio × Wheel circumference (m)
- Gain Ratio = (Wheel radius ÷ Crank length) × (Chainring ÷ Sprocket)
Gain ratio (Sheldon Brown) is dimensionless: it compares how far the bike travels to how far the pedal moves in its orbit, so unlike gear inches it accounts for crank length. Wheel radius and crank length must be in the same units (the calculator derives the radius from your wheel circumference ÷ 2π).
Working figures for this are collected in our Gear Ratios reference table.
Frequently Asked Questions
Gear ratio is the number of times the rear wheel turns for each pedal revolution. A 50/17 gear has a ratio of 2.94, meaning the rear wheel turns 2.94 times per pedal turn.
Typical road setups range from about 1.5 (easy climbing) to 4.5 (fast descending). A 50/17 (2.94) is a good all-round flat riding gear.
Gear inches = Gear ratio x Wheel diameter (in inches). It represents the equivalent wheel diameter of a directly-driven penny-farthing bicycle. Higher gear inches = harder gear.
Development is the distance the bike travels per pedal revolution. Development (m) = Gear ratio x Wheel circumference (m). A higher development means you travel further per pedal turn.
Related Calculators
Cassette Calculator
Analyse cassette tooth counts and gear jumps between sprockets.
Hub Gear Calculator
Calculate effective gear ratios for internal hub gear systems.
Gear Inch Calculator
Calculate gear inches, development in metres and speed at 80, 90 and 100 rpm for any chainring, cog, wheel size and tyre width combination.
Gear Inches Calculator
Convert gear ratios to gear inches for comparison.
Development Calculator
Calculate distance travelled per pedal revolution for any gear.
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Last updated: June 2026
All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.