Bike Gear Calculator
Compare bicycle gearing: enter your chainrings, cassette, wheel and tire size, and cadence to get the ratio, gear inches, metres of development, gain ratio and road speed for every chainring and cog combination.
Last updated:
1 to 3 rings, separated by commas.
All cogs, separated by commas or spaces.
How to use the Bike Gear Calculator
- Enter your chainrings, separated by commas (e.g. 50, 34).
- Enter the cassette cogs, or pick a preset drivetrain.
- Choose the wheel size and tire width.
- Set your cadence and crank length.
- Read the gear range and top speed, then compare every gear in the table and chart.
Bike gearing formulas
| Measure | Formula | 50×11, 700×28 wheel |
|---|---|---|
| Gear ratio | chainring teeth ÷ cog teeth | 4.55 |
| Wheel diameter | rim BSD + 2 × tire width | 622 + 56 = 678 mm (26.7 in) |
| Gear inches | ratio × wheel diameter (in) | 121.3 |
| Development | ratio × π × wheel diameter | 9.68 m |
| Gain ratio | ratio × wheel radius ÷ crank length | 8.93 (172.5 mm cranks) |
| Speed | development × cadence × 60 ÷ 1000 | 52.3 km/h at 90 rpm |
Common wheel sizes (ISO bead seat diameter)
| Name | BSD | Typical tire | Approx. circumference |
|---|---|---|---|
| 700c / 29" | 622 mm | 700×25 | 2,111 mm |
| 700c / 29" | 622 mm | 700×28 | 2,130 mm |
| 700c gravel | 622 mm | 700×40 | 2,205 mm |
| 29" MTB | 622 mm | 29×2.4 (60 mm) | 2,331 mm |
| 650b / 27.5" | 584 mm | 27.5×2.25 (57 mm) | 2,193 mm |
| 26" MTB | 559 mm | 26×2.1 (54 mm) | 2,095 mm |
| 20" BMX | 406 mm | 20×1.75 (44 mm) | 1,552 mm |
| 16" Brompton | 349 mm | 16×1.35 (35 mm) | 1,316 mm |
Calculated circumferences are slightly larger than measured rollout because tires deform under load. For exact speed matching with a bike computer, measure one wheel revolution and enter the equivalent tire width.
Frequently asked questions
How do I calculate bike gear ratio?
Divide the number of teeth on the chainring by the number of teeth on the rear cog. A 50-tooth ring with an 11-tooth cog is 50 ÷ 11 = 4.55: the rear wheel turns 4.55 times for each pedal revolution.
What are gear inches?
Gear inches = gear ratio × wheel diameter in inches. The number is the diameter of an old high-wheel bicycle that would travel the same distance per pedal stroke. Road bikes typically span about 30 to 130 gear inches.
What is gear development (metres of development)?
Development is how far the bike moves per crank revolution: gear ratio × wheel circumference. A 50×11 gear on a 700×28 wheel moves about 9.68 m per revolution. Junior racing rules limit development.
How fast will I go in a gear?
Speed = development × cadence. At 90 rpm in 50×11 on a 700×28 wheel: 9.68 m × 90 × 60 ≈ 52.3 km/h (32 mph). The table also shows each gear at 60 and 110 rpm.
What is gain ratio?
Gain ratio, proposed by Sheldon Brown, is the distance the bike travels divided by the distance the pedal travels: gear ratio × wheel radius ÷ crank length. It accounts for crank length as well as wheel size.
How is wheel circumference calculated?
The tool uses the ISO/ETRTO sizes: diameter = rim bead seat diameter (BSD) + 2 × tire width, and circumference = π × diameter. A 700×28 (622 mm BSD) wheel is about 678 mm across and 2,130 mm around. Measured rollout varies slightly with tire pressure and load.
How is this different from a general gear ratio calculator?
A general gear ratio calculator works with any two gears or a gear train. This tool is made for bicycles: it combines chainrings and a full cassette with wheel size, tire width, crank length and cadence to give gear inches, development and road speed.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.