BMX Gear Calculator

Gear Calculator

Pick your chainring, cog and tyre for gear inches and rollout — or type in the gear you want and we'll find every combo that gets you there.

Gear inches
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Rollout
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inches per crank rev
Gear ratio
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chainring ÷ cog
Tyre diameter
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inches (outside)
Chainrings across, cogs down. Tap a cell to select it. Green cells are within ±1″ of your current gear.

Type the gear you want

Enter gear inches or rollout — they update each other.

Found your gear? Grab the parts to run it.
Race chainrings Rear cogs Sprockets Race tyres

Gear inches

The classic way to compare BMX gearing. Bigger number = harder to turn, faster top end. Most riders sit between 53″ and 57″; the old-school baseline is 44/16 on a 20″ wheel, which is 55″ on the nominal chart (roughly 54″ on a real tyre).
(chainring ÷ cog) × tyre diameter

Rollout

How far the bike travels for one full turn of the cranks. Same information as gear inches, just expressed as a distance. Handy if you think in metres.
(chainring ÷ cog) × tyre diameter × π

Why tyre size matters

A "20 inch" tyre isn't 20 inches. A 20×1.75 measures about 19.5–19.9″ outside, a 20×1 3/8 about 20.5″. That's up to a full gear inch of difference on the same chainring and cog, so charts that assume 20.0″ read a touch high. Use Custom and measure your own wheel for the most accurate number.

Accuracy

Tyre diameters here are typical measured values across common race tyres. Real-world numbers move with pressure, rim width and wear, so treat this as a very close guide rather than gospel.
LUXBMX Gear CalculatorAustralia's BMX experts