Bike gear ratio & development
Ratio, development, gear inches and speed for your drivetrain.
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Single combination
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Cassette table
How it's calculated
Development is how many metres you travel with one full pedal stroke.
- Ratio = chainring teeth ÷ sprocket teeth
- Development (m) = ratio × wheel circumference (m)
- Gear inches = ratio × wheel diameter (inches)
- Speed (km/h) = development × cadence (rpm) × 60 ÷ 1000
E.g. 50×15 with a 700×25c wheel (≈2.11 m): ratio 3.33 → development ≈ 7.0 m; at 90 rpm ≈ 38 km/h.
Common wheel circumferences
| Size | Circumference (mm) |
|---|---|
| 700×25c | 2111 |
| 700×28c | 2136 |
| 700×32c | 2155 |
| 700×35c | 2168 |
| 700×40c | 2200 |
| 650b×47 (gravel) | 2090 |
| 26×2.0 | 2055 |
| 27.5×2.1 | 2148 |
| 29×2.2 | 2298 |
Useful tips
- Low gear (easy) = easier climbing; high (hard) = faster on the flat.
- Typical cadence: 80–100 rpm.
- Compare gears across chainrings to avoid duplicates (overlap).