Bike gear ratio calculator
Bicycle gear ratio and the distance covered per pedal revolution.
Fill in the fields and the result will appear here automatically.
The front-to-rear tooth ratio describes the chain transmission. With direct drive it equals wheel turns per pedal revolution; an internally geared hub needs an additional ratio that this form does not include. Enter wheel circumference in metres to obtain development, the distance per pedal revolution.
How it works
Formula and logic
R = front teeth / rear teeth. Development L = R×C, with wheel circumference C in metres. For direct drive at cadence n rpm, speed in km/h = L×n×0.06; cadence is not entered in this form.
Example
50/25 = 2.00. With C=2.10 m, development is 4.20 m. At 90 pedal revolutions per minute, 4.20×90×0.06 = 22.68 km/h, ignoring slip and additional gearing.
Fields and units
- Chainring teeth — unitless
- Sprocket teeth — unitless
- Wheel circumference — m
How to use
- — Enter positive whole tooth counts for both sprockets.
- — For development, enter measured wheel rollout in metres, for example 2.10.
- — Blank circumference or zero leaves the ratio alone; negative or nonnumeric values are rejected.
- — Check that the drivetrain does not add an internal gear stage.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- Schwalbe: construction, rim, pressure and load affect rollout Shimano 2026–2027 specifications: additional internal hub gear ratios
- Limitation
- Direct chain-drive model. Internal hubs, reduction gears, slip and motion resistance are excluded; this does not check component compatibility.
FAQ
What does a bicycle tooth ratio mean?
R=2 gives two wheel turns per pedal revolution only with direct drive and no additional internal ratio.
Why compare gear development?
It accounts for wheel size: equal ratios can produce different distances per pedal revolution.
How do I measure circumference for development?
At working pressure and load, mark the tyre and measure one complete rollout. Divide millimetres by 1000 for metres.
Why must sprocket teeth be whole numbers?
They count discrete teeth. Fractional and nonnumeric counts are rejected.
Which gear is appropriate for a climb?
Lower development requires more pedal revolutions for the same distance. The suitable value depends on slope, load and rider.
How does cadence convert to speed?
Cadence is pedal revolutions per minute. 4 m development × 90 rpm = 360 m/min = 21.6 km/h; no universal required cadence is prescribed.
Does gear count determine a useful range?
No. Combination count does not describe extreme ratios, duplicate steps or internal gearing; compare actual developments.