CalculatorsGear Inches and Roll-out Calculator

Gear Inches and Roll-out Calculator

Gear inches multiply the ratio by the wheel diameter. Roll-out is the metres the bike travels in one crank revolution — the number that tells you whether 52×11 on a 700×28c is actually a fast gear.

Inputs

Chainring teethCog teethWheel

Results

Gear inches: 126.2 in
Roll-out: 33.04 ft

How the number is made

Diameter mm = bead seat diameter + 2 × labelled tyre width. Gear inches = (chainring ÷ cog) × diameter ÷ 25.4. Roll-out (m) = ratio × π × diameter ÷ 1000.

Labelled width stands in for tyre height. A wide rim can make the real tyre taller.

Related calculators

Bicycle Gear Ratio Calculator
Strip the wheel back out and compare chainrings directly.
Wheel Circumference Calculator
The GPS millimetre figure behind this roll-out.

Questions

What is a high gear inch?

Road 52×11 on 700×28c is roughly 125 gear inches. A 34×51 on a 29er is under 30.

Is roll-out the same as gear inches?

They describe the same gear in different units. Roll-out is a distance; gear inches are a historic diameter.

Why does a wider tyre raise gear inches?

Roll-out uses labelled tyre width on top of the rim diameter. A 28 mm tyre on a 622 mm bead is treated as a 678 mm diameter.

Related gear

GPS bike computer
Roll-out in millimetres is the calibration figure for a speed sensor.
$200–$700

Disclaimer — no professional advice, no liability

These calculators are simplified estimates for education. They are not a bike fit, a structural inspection, or a torque specification that overrides the number printed on a part. Confirm chain length, spoke length, tire fit and bolt torque on the bicycle before you ride.

These calculators, pages and any related content are provided “as is” and “as available”, solely for general educational and informational purposes. They are simplified mathematical estimates, not a professional bike fit, a structural inspection, a manufacturer torque specification or a training, nutrition or medical plan.

Results can be wrong, incomplete or inapplicable to your frame, wheels, tires, drivetrain or suspension. You must independently verify every figure, assume all risk, and confirm chain length before you cut, spoke length before you lace, tire and rim compatibility before you inflate, and the torque printed on the part before you tighten it.

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