Bike Gear Calculator (Gear Inches, Development, Speed)
Enter the chainring and sprocket teeth, wheel diameter and cadence.
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Bike Gear Calculator (Gear Inches, Development, Speed) by TheCalcTools
How the Bike Gear Calculator (Gear Inches, Development, Speed) works
Gear inches = wheel diameter × chainring ÷ sprocket: the diameter of an old high-wheeler with the same gearing. Development is the distance travelled per pedal turn, gear inches × π.
Speed = development × cadence. Compare gearing across bikes with different wheel sizes using gear inches or development.
The formula
Worked example
Using the default values shown in the calculator:
| Chainring teeth | 50 |
|---|---|
| Rear sprocket teeth | 17 |
| Wheel diameter with tyre (in) | 26.3 |
| Cadence (RPM) | 90 |
- 50 × 17 on a 26.3 in wheel: 77.4 gear inches, 6.17 m per turn.
- At 90 RPM that is 33.3 km/h.
Result:
| Gear inches | 77.4 |
|---|---|
| Development (m per pedal turn) | 6.17 |
| Gear ratio | 2.941 |
| Speed at the cadence (km/h) | 33.3 |
| Speed at the cadence (mph) | 20.7 |
Frequently asked questions
What is a typical climbing gear?
Road bikes often go down to about 30 to 35 gear inches; mountain bikes below 20.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.