Cycling Gear Ratio Calculator
Calculate bicycle gear ratio, chain development, and speed at any cadence from chainring and cassette.
Covers road, gravel, MTB, and single-speed setups.
How Cycling Gear Ratio Is Calculated
Gear ratio determines how far your bike travels with each pedal revolution. It’s the fundamental relationship between chainring teeth and sprocket teeth.
Gear Ratio Formula:
Gear Ratio = Chainring Teeth / Sprocket Teeth
Development (Distance Per Pedal Revolution):
Development (m) = Gear Ratio × Wheel Circumference
For a 700c wheel, circumference ≈ 2.096 m (standard road tire at 23–25mm width).
Worked Example: A road bike with a 50-tooth chainring and 12-tooth sprocket:
- Gear Ratio = 50 / 12 = 4.17
- Development = 4.17 × 2.096 = 8.74 meters per pedal stroke
At 90 RPM cadence: 8.74 × 90 × 60 = 47,196 m/hr = 47.2 km/h
Common Gear Ratio Reference:
- 34/34 (1:1) — steep mountain climbing
- 39/25 (1.56:1) — moderate climbing
- 50/17 (2.94:1) — all-day cruising
- 53/11 (4.82:1) — sprinting, descent
Optimal Cadence by Discipline:
- Road cycling: 85–100 RPM
- Mountain biking: 70–90 RPM
- Track sprinting: 110–130 RPM
Chainline Note: Avoid extreme cross-chaining (big chainring + big sprocket, or small + small) — it wastes energy and accelerates chain wear. Most efficient gear pairs keep the chain nearly straight.
Gear Inches (Alternative Measurement):
Gear Inches = (Chainring / Sprocket) × Wheel Diameter (inches)
A 700c wheel is approximately 27 inches in diameter. Gear inches is commonly used in velodrome (track) cycling to compare single-speed setups.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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