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
Results
- Gear inches
- 126.2 in
- Roll-out
- 33.04 ft
The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.
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. Example: 52×11 on 700×28c → 678 mm, 126.2 gear inches, 10.07 m.
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 about 126 gear inches. A 34×51 on a 29 × 2.25 wheel is about 19.
Is roll-out the same as gear inches?
They describe the same gear in different units. Gear inches are the diameter of an equivalent penny-farthing wheel; roll-out is the distance one crank turn moves you. Roll-out (m) = gear inches × π × 0.0254.
Why does a wider tyre raise gear inches?
Both numbers use the wheel diameter, and the tyre adds its labelled width above and below the 622 mm bead seat. A 28 mm tyre gives 678 mm; a 32 mm tyre gives 686 mm, about 1.2% more gear.
Example products
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- GPS bike computer
Set its wheel size to the wheel circumference in millimetres, not to this roll-out.
$200–$700