Bicycle Gear Ratio + Gear Inches Calculator
Ratio = front teeth / rear teeth. Gear inches = ratio × wheel diameter (in).
Result
Loading calculator…
—
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.
Related calculators
Cycling Pace / Time Calculator
Time = distance / speed. Convert any of {distance, speed, time} given the other two.
Cycling Power-to-Weight Calculator
W/kg = sustained power (W) / body weight (kg). Maps to USAC category and Coggan rider type.
Gradient (Grade %) Calculator
Grade % = rise / run × 100. Convert to angle (degrees) and category (Cat 4-HC).
Cycling Calorie Burn by Power Calculator
kcal ≈ avg watts × hours × 3.6 — direct from work done (kJ ≈ kcal at 25% gross efficiency).
Running Cadence Calculator
Convert between cadence (steps per minute), stride length, and running speed.
FTP from 20-Minute Test Calculator
Functional Threshold Power = 20-min average power × 0.95. The standard cycling test protocol.