Gear Inches Calculator
Gear inches normalize your gear ratio based on wheel size. It represents the equivalent diameter of a direct-drive wheel (like a Penny Farthing).
Bike Details
Front chainring size.
Rear cassette cog or freewheel size.
*Calculations assume standard tire profiles. For exact precision, measure your wheel diameter floor-to-top.
Gear Inches
One pedal stroke moves you as far as one rotation of a 72.3 inch wheel.
Why Calculate Gear Inches?
Standard Gear Ratios are useful, but they have a flaw: they ignore the size of your wheels. A 32/18 gear on a 20-inch BMX bike feels much easier than the exact same 32/18 gear on a 29-inch Mountain Bike.
Gear Inches solve this by factoring in wheel diameter. This gives you a universal number to compare "how hard it feels to pedal" across any bike—whether it's a folding bike, a road racer, or a monster gravel rig.
The Formula
Gear Inches = (Chainring ÷ Cog) × Wheel Diameter
*Wheel Diameter is measured in inches, including the tire.
Reference Guide: What is a "Good" Gear Inch?
Use this chart to determine if your gearing setup is suitable for your riding style.
| Gear Inches | Difficulty | Best For |
|---|---|---|
| Below 25" | Very Easy | Steep MTB Climbing, Loaded Touring |
| 40" - 55" | Easy / Moderate | Casual City Riding, Gravel Hills |
| 65" - 75" | Standard | Single Speed Road, Flat Commuting |
| 90" + | Hard / Fast | Road Sprinting, Fast Descending |
Real World Example
Imagine you are converting a 26" mountain bike into a commuter and want it to feel like your road bike.
- Road Bike: 42t chainring / 16t cog on 700c wheels = ~69 Gear Inches.
- 26" MTB: To get the same 69" feel on smaller 26" wheels, you would need a harder gear ratio, roughly 48t / 18t.
Without calculating gear inches, you might just use the same 42/16 ratio on the MTB, which would result in 63 gear inches—feeling significantly slower and "spinnier."