🚲 Bike Gear Ratio Calculator

Enter chainring (front) and sprocket (rear) tooth counts, wheel size, and cadence to compute gear ratio, gear inches, rollout (development distance), and speed for every combination.

Chainring Teeth (front, comma-separated)

Sprocket Teeth (rear, comma-separated)

Wheel / Tire Size

Cadence (RPM)

Featured Gear (highest chainring × lowest sprocket)

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Gear Ratio — Gear Inches — Rollout (m/rev) —

Full Gear Combination Table

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GUIDE

Learn more

What Gear Ratio and Gear Inches Mean in Cycling

Gear ratio is the chainring tooth count divided by the sprocket tooth count, showing how many times the rear wheel turns per single pedal revolution. A 50-tooth chainring paired with a 17-tooth sprocket gives a ratio of 50÷17≈2.94 — one pedal stroke spins the rear wheel about 2.94 times. Gear inches multiplies that ratio by the wheel diameter in inches, a unit inherited from penny-farthing high-wheelers, and it lets you compare gearing "heaviness" across bikes with completely different wheel sizes. Road bikes typically span roughly 30-130 gear inches, mountain bikes 20-100, with lower numbers for climbing and higher numbers for flats and descents.

How Cadence and Gearing Together Determine Your Speed

Development (rollout) is the actual forward distance the bike travels per pedal revolution, found by multiplying wheel circumference (π × diameter) by the gear ratio. Multiply that by your cadence (pedal revolutions per minute) and convert units, and you get instantaneous speed. For example, a 700x23c wheel (diameter ≈682mm, circumference ≈2.14m) with a 50/17 gear ratio of 2.94 yields a rollout of about 6.30m per revolution; at 90rpm cadence that works out to roughly 34km/h. Keep cadence constant and speed scales directly with gear ratio and wheel size — bigger gears or bigger wheels mean more ground covered per pedal stroke.

Frequently asked questions

What is a good gear ratio for climbing versus flat riding?

For climbing, a low gear ratio around 1.0 or below (e.g. 34T/32T) helps you spin at a sustainable cadence without burning out your legs. For flats and descents, a higher ratio of 3.0-4.5+ (e.g. 50T/12T) lets you push more speed per pedal stroke. Matching your cassette range to your fitness and typical terrain grade gives you flexibility across conditions.

Why is "gear inches" still used as a unit?

Gear inches dates back to 19th-century high-wheel (penny-farthing) bicycles, where the front wheel was directly driven by the pedals with no chain — the unit described what wheel diameter would produce the same pedaling feel. Modern chain-driven bikes inherited the unit because it still lets you compare gearing heaviness across road, mountain, and folding bikes that use completely different wheel diameters, on one consistent scale.

How much does wheel size change rollout distance?

Rollout scales directly with wheel circumference, so a larger diameter travels farther per pedal revolution at the same gear ratio and cadence. Switching from a 26-inch to a 29-inch mountain bike wheel, for instance, increases rollout by roughly 10% for the same gearing, which is part of why 29ers feel faster at the same effort.