Calculator Inputs
Formula Used
1) Gear Ratio
Gear Ratio = Front Chainring Teeth ÷ Rear Cog Teeth
2) Gear Inches
Gear Inches = Gear Ratio × Wheel Diameter in Inches
3) Wheel Circumference
Wheel Circumference = π × Wheel Diameter
4) Development or Rollout
Development = Gear Ratio × Wheel Circumference
5) Speed
Speed (km/h) = Development × Cadence × 60 ÷ 1000
6) Gain Ratio
Gain Ratio = Gear Ratio × Wheel Radius ÷ Crank Length
These formulas help riders compare climbing ease, sprint potential, and cadence demands across chainring, cassette, and wheel-size combinations.
How to Use This Calculator
- Enter your front chainring teeth and rear cog teeth values.
- Provide the effective wheel diameter and choose inches or millimeters.
- Set cadence, crank length, and optional target speed for cadence planning.
- Use comparison lists to test multiple chainring and cassette options.
- Press the calculate button to show results above the form.
- Review the summary cards, comparison table, and speed-versus-cadence graph.
- Export the calculated data using the CSV or PDF buttons.
Example Data Table
| Chainring | Rear Cog | Wheel | Cadence | Ratio | Gear Inches | Speed (km/h) |
|---|---|---|---|---|---|---|
| 34T | 28T | 27.5 in | 80 rpm | 1.214 | 33.39 | 12.79 |
| 39T | 17T | 27.5 in | 90 rpm | 2.294 | 63.09 | 27.18 |
| 50T | 15T | 27.5 in | 95 rpm | 3.333 | 91.67 | 41.69 |
| 52T | 11T | 27.5 in | 100 rpm | 4.727 | 130.00 | 62.24 |
Example values illustrate climbing, balanced, and high-speed setups. Your actual results depend on tire size, effective diameter, and exact cadence.
FAQs
1) What does bike gear ratio mean?
Bike gear ratio shows how many rear wheel turns occur per crank turn. A higher ratio usually means more speed potential but harder pedaling.
2) Is a higher gear ratio always better?
No. Higher ratios help fast riding on flatter terrain, while lower ratios improve climbing and reduce leg strain on steep gradients or long endurance rides.
3) What are gear inches?
Gear inches combine gearing and wheel size into one value. They make it easier to compare different bikes, wheel diameters, and drivetrain combinations.
4) Why does wheel diameter matter?
Larger effective wheel diameter increases rollout and speed for the same ratio. Smaller wheels shorten distance traveled per crank revolution.
5) How does cadence change my speed?
At a fixed gear, speed rises directly with cadence. Doubling cadence nearly doubles speed, assuming wheel slip and drivetrain losses stay similar.
6) What is gain ratio useful for?
Gain ratio includes crank length and wheel radius, so it compares pedal leverage more precisely than simple tooth-count ratio alone.
7) Can I compare several chainrings and cogs together?
Yes. Enter comma-separated chainring and cog lists. The calculator builds a comparison table and graph for quick setup evaluation.
8) Should I use tire labeled size or measured diameter?
Measured effective diameter is better. Actual tire width, pressure, and rim design can shift the real rolling diameter away from the label.