Bike Gear Calculator
Calculate gear ratio, gear inches, development and speed at cadence for any chainring, cog and wheel.
Loading calculator…
What this tool does
Calculate gear ratio, gear inches, development and speed at cadence for any chainring, cog and wheel. Wheel diameter is the overall diameter including the tyre (about 26.5 in for 700×25, 27.9 in for 700×38 gravel). Speed assumes you can hold the entered cadence in that gear on the flat.
How to use the Bike Gear Calculator
- Enter or select chainring teeth.
- Enter or select rear cog teeth.
- Enter or select overall wheel diameter (inches).
- Enter or select cadence (rpm).
- Read the calculated result; change any measurement to compare alternatives.
Formula
gear ratio = chainring ÷ cog; gear inches = ratio × wheel diameter (in); development = ratio × π × wheel diameter; speed = cadence × gear inches × π × 60 ÷ 63,360 (mph)
- ring
- Chainring teeth
- cog
- Rear cog teeth
- wheel
- Overall wheel diameter (inches)
- cadence
- Cadence (rpm)
Wheel diameter is the overall diameter including the tyre (about 26.5 in for 700×25, 27.9 in for 700×38 gravel). Speed assumes you can hold the entered cadence in that gear on the flat.
Worked example
For bike gear calculator, the following measurements illustrate the exact method: Chainring teeth: 52; Rear cog teeth: 16; Overall wheel diameter (inches): 26.5; Cadence (rpm): 90.
Inputs
- Chainring teeth52
- Rear cog teeth16
- Overall wheel diameter (inches)26.5
- Cadence (rpm)90
Result
- Gear inches86.13
- Gear ratio3.25
- Development (meters per crank revolution)6.87
- Speed at cadence (mph)23.06
- Speed at cadence (km/h)37.11
Results explained
- Gear inches
- Gear inches from the formula above. Wheel diameter is the overall diameter including the tyre (about 26.5 in for 700×25, 27.9 in for 700×38 gravel). Speed assumes you can hold the entered cadence in that gear on the flat.
- Gear ratio
- Gear ratio from the formula above. Wheel diameter is the overall diameter including the tyre (about 26.5 in for 700×25, 27.9 in for 700×38 gravel). Speed assumes you can hold the entered cadence in that gear on the flat.
- Development (meters per crank revolution)
- Development (meters per crank revolution) from the formula above. Wheel diameter is the overall diameter including the tyre (about 26.5 in for 700×25, 27.9 in for 700×38 gravel). Speed assumes you can hold the entered cadence in that gear on the flat.
- Speed at cadence (mph)
- Speed at cadence (mph) from the formula above. Wheel diameter is the overall diameter including the tyre (about 26.5 in for 700×25, 27.9 in for 700×38 gravel). Speed assumes you can hold the entered cadence in that gear on the flat.
- Speed at cadence (km/h)
- Speed at cadence (km/h) from the formula above. Wheel diameter is the overall diameter including the tyre (about 26.5 in for 700×25, 27.9 in for 700×38 gravel). Speed assumes you can hold the entered cadence in that gear on the flat.
Frequently asked questions
The diameter of the imaginary penny-farthing wheel that would travel the same distance per pedal turn. It folds chainring, cog and wheel size into one comparable number across bikes.
Road bikes span roughly 30 (low climbing gear) to 135+ (52×11 sprint gear). Gravel and MTB setups go down near 20 for steep off-road climbs.
Linearly — double the cadence, double the speed. That is why the calculator asks for cadence: gear inches alone can't give a speed.
Development is the distance travelled per crank revolution. Junior racing rules cap it (rollout limits) to protect young riders, so it is checked by rolling the bike one full pedal turn.
Yes — the same 52×16 on a larger wheel is a bigger gear. Switching from 700×25 to 700×38 tyres adds roughly 5% to every gear inches value.