Bike Gear Ratio Calculator
Work out your gear ratio, gear inches, and development from your chainring, cog and wheel size.
How to use the gear ratio calculator
- Enter your chainring and cog (sprocket) teeth.
- Pick your wheel and tire size.
- Click Calculate to see ratio, gear inches and development.
Ratio, gear inches and development
Gear ratio is simply chainring teeth divided by cog teeth. Gear inches and development translate that into real-world distance per pedal revolution, which is what actually determines how the gear feels.
Gear ratio, gear inches, and development
Gear ratio is simply chainring teeth divided by cog teeth, but cyclists also use gear inches and development (metres rolled per pedal revolution) to compare gearing across different wheel sizes. These let you judge whether a setup will feel easy enough for steep climbs or tall enough for fast descents.
Choosing gearing for your terrain
Hilly riders favour lower gears (a smaller chainring or larger cassette) to keep cadence comfortable on climbs, while flat-terrain and racing riders may want taller gears for high-speed efforts. Comparing development figures across options helps you pick a setup that matches your terrain and pedalling style.
Frequently asked questions
What is a good gear ratio for cycling?
It depends on terrain. A 2.5–3.5 ratio suits flat riding, while lower ratios (under 2) help on steep climbs. Gear inches let you compare across wheel sizes.
What are gear inches?
Gear inches express how far the bike travels per pedal stroke relative to wheel size — a legacy measure that lets you compare gearing fairly across different wheels.
What is gear inches?
Gear inches expresses a gear as the diameter of a wheel that would roll the same distance per pedal turn on a direct-drive bike. Higher numbers mean a taller, harder gear.
What gearing is best for climbing?
Lower gears, achieved with a smaller chainring or a larger-range cassette, let you spin a comfortable cadence on steep gradients instead of grinding.
How do I compare gears between bikes with different wheels?
Use gear inches or development rather than raw ratio, because those account for wheel size and give a true comparison.
Related tools
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See how fast a gear and cadence combination will move you, in km/h and mph.
Wheel Circumference Calculator
Get the circumference value to enter into your bike computer, by tire size or measured diameter.
Power-to-Weight Calculator
Calculate your watts per kilogram (W/kg) — the number that best predicts climbing and racing performance.