Bicycle Gear Calculator
Development, gear ratio, gear inches and road speed for a chainring and sprocket combination.
Results
Development per pedal turn
7.486
m
Gear ratio
3.5714
Gear inches
93.81
in
Speed
40.42
km/h
Pedalling cadence
66.8
rpm
What this tool does
Development is the distance covered by one turn of the pedals, which is the most intuitive way to compare gears: 7.5 metres is a fast road gear, 2.5 metres a low climbing one. Gear inches is the older measure and still what most cycling charts use. A 700×25C tyre rolls about 2096 mm per turn.
Formula
development = (teeth à front ÷ teeth rear) × wheel circumference
Variables
| Symbol | Meaning | Unit |
|---|---|---|
ch | Chainring teeth | — |
sp | Sprocket teeth | — |
wc | Wheel rolling circumference | mm |
cd | Pedalling cadence | rpm |
DV | Development per pedal turn | m |
GR | Gear ratio | — |
GI | Gear inches | in |
SP | Speed | km/h |
CA | Pedalling cadence | rpm |
Worked example
- Chainring teeth50
- Sprocket teeth14
- Wheel rolling circumference2096 mm
- Pedalling cadence90 rpm
- Development per pedal turn7.486 m
- Gear ratio3.5714
- Gear inches93.81 in
- Speed40.42 km/h
- Pedalling cadence66.8 rpm
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.