Bike Gear Ratio Calculator
Build a full gear chart from your chainrings and cassette: gear ratios, gear inches, development, gain ratio and speed at any cadence.
- Gear combinations
- 20
- Lowest gear
- 1.21
- Highest gear
- 4.55
- Gear range
- 374%
- Wheel
- 2105 mm · 26.4" ⌀
| Gear ratio | 11t | 12t | 13t | 14t | 15t | 17t | 19t | 21t | 24t | 28t |
|---|---|---|---|---|---|---|---|---|---|---|
| 50t | 4.55 | 4.17 | 3.85 | 3.57 | 3.33 | 2.94 | 2.63 | 2.38 | 2.08 | 1.79 |
| 34t | 3.09 | 2.83 | 2.62 | 2.43 | 2.27 | 2.00 | 1.79 | 1.62 | 1.42 | 1.21 |
How it works
Your bike's gear ratio is simply the chainring teeth divided by the cog teeth: a 50-tooth chainring with an 11-tooth cog gives a ratio of 4.55, so the rear wheel turns 4.55 times for every turn of the pedals. Enter your chainrings and your cassette and the calculator builds the whole chart at once, then converts it into the other numbers riders actually compare: gear inches (ratio × wheel diameter in inches), development (metres travelled per pedal revolution), speed at your chosen cadence, and Sheldon Brown's gain ratio, which also accounts for crank length so you can compare bikes with different cranks fairly.
Pick your wheel and tyre to set the rolling circumference (or type a custom value straight off your bike computer), set a cadence, and the summary shows your lowest and highest gear plus the total gear range — the percentage that tells you how much easier your climbing gear is than your top gear. Everything is plain JavaScript running in your browser: your setup is never uploaded, and there are no ads or sign-ups.
Frequently asked questions
How do you calculate a bike gear ratio?
Divide the number of teeth on the front chainring by the number of teeth on the rear cog. A 50-tooth chainring with an 11-tooth cog gives 50 ÷ 11 = 4.55, meaning the rear wheel turns 4.55 times for every full turn of the pedals. A 34-tooth chainring with a 28-tooth cog gives 34 ÷ 28 = 1.21, a much easier climbing gear. This calculator works out every chainring and cog combination at once so you can see your whole range in one chart.
What are gear inches, development and gain ratio?
They are three ways of turning a raw ratio into something you can feel. Gear inches multiply the ratio by your wheel diameter in inches (ratio × wheel diameter), the traditional way to compare gears across bikes. Development is how far you actually travel in metres for one pedal revolution (ratio × rolling circumference). Gain ratio, devised by Sheldon Brown, divides the wheel radius by your crank length before multiplying by the ratio, so it also accounts for the leverage your cranks give you — the only fair comparison between bikes with 165 mm and 175 mm cranks.
What is a good gear range for climbing?
Gear range is your highest ratio divided by your lowest, expressed as a percentage — a 50/34 chainset with an 11–28 cassette gives about 374%. For steep climbs what matters is the lowest gear: a ratio at or below 1.0 (a 1:1 or easier gear, roughly 30 gear inches) lets most riders spin up gradients over 10% without grinding. Modern 1× gravel and mountain setups often reach 0.7 or lower. Use the chart to check your smallest chainring against your biggest cog before you commit to a hilly route.