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GEAR RATIO CALCULATOR

Every chainring and cog combination mapped to gear ratio, gear inches, development, and speed at cadence. See where your gearing overlaps and where the gaps are.

Quick presets

Selected: 50/34T

METHODOLOGY

Gear ratio: Chainring teeth divided by cog teeth. A 50/25 combination gives a ratio of 2.0 — each pedal revolution turns the rear wheel twice.

Gear inches: Gear ratio multiplied by the wheel diameter in inches. An old standard (dating back to penny-farthing comparisons) that remains the most intuitive way to compare gears across different wheel sizes.

Meters of development: Gear ratio multiplied by the wheel circumference (rollout) in meters. This is the distance the bike travels per pedal revolution. Widely used in continental Europe and in track cycling.

Rollout variation: The tyre circumferences used here assume standard inflation and no load deformation. Real-world rollout varies with tyre pressure, rider weight, and tyre construction. A 2-3% difference is typical. For precision, measure your own rollout — mark the tyre, ride one revolution, measure the ground distance.

Source:The formulas follow Sheldon Brown's canonical gear-calculation methodology. Brown's work remains the definitive reference for bicycle gearing arithmetic.

Last updated: July 2026 · Tool version 1.0

FROM HERE

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