Online Gear Calculator / Roll Out Calculator for Derailleurs


This gear calculator should help you with the design of the derailleur system on your bicycle. Simply adjust the data of the bike and then click on "Calculate tables and graph".

The number of teeth of the chainring and the sprocket can be entered in any order, the numbers are sorted during the calculation.

The wheel circumference can be entered freely or you choose the tire size from the list.

The "forbidden" (red) ratios due to excessive skew can be set.

The tables then show the transmission ratio and the roll out, i.e. the distance travelled in one complete crank revolution, and the speed at the set pedaling speed. The colours: red: transmission not good due to excessive skew of the chain; yellow: transmission with overlap; green: transmission ok.

The graphics can be copied to the bottom of the page for comparison and positioned as desired using "Drag and Drop".

Data of the Bike

Number of teeth on the chainring: .

, so that the gradation is as even as possible, or enter the values:

Number of teeth on the sprockets: .

This results in a ratio bandwidth of  , and a gearbox with a capacity of   teeth is required.

, or . revolutions per minute.

Transmission ratio / Roll out
in meters per crank turn

Speed in km/h


Link to Current Configuration

The following link leads directly to the currently set configuration. You can copy it or add it to your bookmarks.

11. 11. 2023, Jürgen Berkemeier



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Parameter Error

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Deutsche Version