Online Tool Store
Bike Gear Inches Calculator
Enter chainring teeth, rear cog teeth, and wheel size to calculate gear inches. Runs entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Gear inches
Example shown — replace it with your own gearing and wheel size.
How it works
- Enter your chainring and rear cog tooth counts.
- Enter your wheel size in inches.
- See the gear inches value instantly.
Calculation multiplies wheel diameter by the ratio of chainring teeth to rear cog teeth — the traditional gear inches formula cyclists have used since the days of penny-farthings to compare gearing across different bikes.
FAQ
Is my gearing data uploaded anywhere?
No. The calculation happens entirely in your browser — nothing is sent to a server.
What is "gear inches"?
A single number representing effective wheel diameter for a given gear combination — the traditional way cyclists compare gearing across different wheel sizes and drivetrains.
How is it calculated?
Wheel diameter × (chainring teeth ÷ rear cog teeth) — a formula dating back to high-wheel bicycles, still used today for comparing overall gear ratios.
Why not just compare chainring-to-cog ratios directly?
Wheel size affects how far a gear ratio actually moves you per pedal stroke — gear inches accounts for that, making comparisons across different bikes meaningful.
How we compare
| Feature | Online Tool Store | Manual formula math | Bike shop gear charts |
|---|---|---|---|
| Works for any custom gearing | ✓ | Easy to make an error | Only covers common preset combinations |
| Free, instant | ✓ | ✓ | ✓ |
A preset gear chart only covers common combinations. Bike Gear Inches Calculator works for any custom chainring, cog, and wheel size.