Bicycle Gear Ratio + Gear Inches Calculator

Ratio = front teeth / rear teeth. Gear inches = ratio × wheel diameter (in).

Inputs

Result

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General calculation reads

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How to use this calculator

  • Read tooth count off chainring and cog.
  • Pick wheel + tire size.
  • Set cadence (90 is recreational standard).
  • Compare gear inches between bikes for fair comparison.

About this calculator

Gear ratio is teeth in front divided by teeth in back. A 50t chainring and 14t cog = 3.57:1, meaning the wheel turns 3.57 times per pedal revolution. Gear inches (US road tradition) multiplies ratio by wheel diameter — useful because it normalizes across wheel sizes. A 50/14 on a 700x25 ≈ 95 gear inches; same ratio on a 26" MTB only ≈ 93. Pros at 90 rpm in 95 gear inches = ~32 mph.

Frequently asked

What's a typical road bike gear range?+
Compact 50/34 × 11-30 = 22.7 to 122 gear inches. A 1:1 lowest ratio (34×34) is the climbing standard now.
What about MTB?+
Modern 1× MTB: 32t front × 10-52 cassette. That's 22-115 gear inches on a 29er — wider than road, lower bottom end.
How is this different from a derailleur calculator?+
This shows one gear at a time. A derailleur calculator shows all combinations + speeds — useful for picking groupset.
What's "gain ratio"?+
Sheldon Brown's improvement: factor in crank length too. Most riders use simple gear inches; gain ratio matters for very different crank lengths.
How does cadence affect speed?+
Speed is linear in cadence at fixed gear. 50/14 at 90 rpm vs. 100 rpm = 11% faster. Gear shifting changes both ratio and speed.

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