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Bike Gear Ratio Calculator

Converts a chainring and sprocket into gear ratio, gear inches, development and gain ratio for any wheel size.

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Enter your figures and press Calculate.
In short A bicycle gear can be written four ways and they all describe the same thing. The gear RATIO is simply the chainring divided by the sprocket, so a 50-tooth ring on a 16-tooth sprocket is 3.125 — the wheel turns 3.125 times for every turn of the cranks. GEAR INCHES multiplies that by the wheel diameter in inches, giving the size of wheel a penny-farthing would need to travel the same distance per pedal stroke; that is genuinely where the number comes from, and it is why the figures look so large. DEVELOPMENT is the same ratio times the wheel circumference, in metres travelled per crank revolution, and it is the number that tells you how fast you will actually be going. Because circumference is π times diameter, development divided by gear inches is always 0.0798 — for every gear, on every bike, with every wheel. GAIN RATIO is the only one of the four that accounts for crank length, which is why it is the fair way to compare bikes with different cranks. Longer cranks give more leverage, so the same gear feels easier, and gear inches cannot see that at all.

How to use the Bike Gear Ratio Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Bike Gear Ratio Calculator

The Bike Gear Ratio Calculator converts a chainring and sprocket into gear ratio, gear inches, development and gain ratio for any wheel size. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Comparing two gears without guessing.
  • Choosing a chainring or cassette before buying.
  • Understanding what gear inches actually mean.

Details

Gear ratioChainring teeth divided by sprocket teeth
Gear inchesRatio × wheel diameter in inches
DevelopmentRatio × wheel circumference, in metres per crank turn
They are linkedDevelopment ÷ gear inches is always 0.0798, on every bike
Tyre height is taken as equal to tyre width. That is a working approximation — a tyre is not a circle, and its fitted height depends on the rim it is mounted on.

Frequently asked questions

What are gear inches?
The diameter of the penny-farthing wheel that would travel the same distance per pedal turn. That is a historical definition, not an analogy, and it is why the numbers run from about 20 to about 130.
Which number should I use?
Gear inches to compare gears on one bike, development if you want metres per pedal stroke, gain ratio if you are comparing bikes with different crank lengths.
Does crank length matter?
Yes, and only gain ratio accounts for it. A longer crank is more leverage, so the same gear feels easier, but gear inches and development cannot see the cranks at all.
Why does my wheel size change the answer?
Because the same gear moves a bigger wheel further. The ratio is unchanged; gear inches and development both scale with the wheel.
Is there a limit on how often I can use the Bike Gear Ratio Calculator?
It is free, with no account, no trial and no daily cap. Every calculators tool on inputtesthub.com works the same way: open the page and use it.
Is my data uploaded anywhere?
No. The Bike Gear Ratio Calculator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
What does a typical result look like?
Enter 50 × 16 on 700 × 25 and the Bike Gear Ratio Calculator returns ratio 3.125, 82.7 gear inches, 6.60 m.
What is the Bike Gear Ratio Calculator used for?
The most common reasons people reach for it: comparing two gears without guessing. Choosing a chainring or cassette before buying. Understanding what gear inches actually mean. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Any caveats I should know about?
Tyre height is taken as equal to tyre width. That is a working approximation — a tyre is not a circle, and its fitted height depends on the rim it is mounted on.
What are the reference figures here?
Gear ratio is Chainring teeth divided by sprocket teeth. Gear inches is Ratio × wheel diameter in inches. Development is Ratio × wheel circumference, in metres per crank turn. These are printed on the page itself, so you do not have to take them on trust.
Is the number rounded?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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