Bicycle Gear Calculator
Free bicycle gear ratio calculator. Compute gear inches, development meters, gain ratios and speed at your cadence from chainring and sprocket teeth, with wheel size presets, crank length and a cassette gear-step table. Runs in your browser.
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What is Bicycle Gear Calculator?
The Bicycle Gear Calculator converts chainring and sprocket tooth counts into the numbers that describe a gear: the ratio, gear inches, development in meters, and the Sheldon Brown gain ratio, plus the road speed you travel at a given cadence. Enter a whole cassette of sprocket sizes and it builds a side-by-side table with the percentage step between neighbouring gears, using wheel presets for road, gravel and mountain bikes or your own exact circumference.
Key Benefits
- One readout with ratio, gear inches, development and gain ratio
- Real-world speed from the cadence you actually hold, in km/h and mph
- Cassette table shows the percentage jump between every neighbouring gear
- Wheel presets for road, gravel and MTB, or the exact circumference from your cycle computer
- Crank length support makes gain ratios comparable across bikes
Common Use Cases
- •Choosing between an 11-34 and a 12-36 cassette for a hilly sportive
- •Checking whether a 1x conversion keeps enough low gear for your trails
- •Matching gearing after switching from 700c to 650b wheels
- •Comparing a 50/34 compact against a 52/36 standard crankset
- •Explaining to a riding buddy why their gear jumps feel harder mid-climb
How to Calculate Bicycle Gear Ratios
- Enter your drivetrain: Type the chainring teeth and the sprocket teeth you want to analyse, for example 50 and 34 for the crossover gear of a road compact crankset.
- Pick the wheel size: Choose the preset that matches your tyre, or switch to custom and enter the circumference your cycle computer uses in millimetres. Wheel size is what turns a ratio into real-world distance.
- Set cadence and crank length: Enter the cadence you hold, say 90 rpm, and your crank length, usually 170 or 175 mm. The crank length feeds the gain ratio, which compares wheel radius to crank arm.
- Compare the whole cassette: List every sprocket in the cassette box to get a table of gear inches, development, speed and the percentage step between neighbours, then look for the jumps that feel hardest to turn.
Key Features
- Gear ratio, gear inches, development meters and gain ratio in one readout
- Speed at your cadence in both km/h and mph
- Cassette table exposing the percentage step between neighbouring sprockets
- Road, gravel and MTB wheel presets from ETRTO sizes, plus custom circumference
- Crank length input for true Sheldon Brown gain ratios
- Copyable results and one-click reset to road defaults