Sheldon Brown's
Derailer Gear/Internal-Gear Calculator
Derailer Gear/Internal-Gear Calculator
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You need to enter data for at least one chainring, and at least
one sprocket unless you choose a stock cassette.
Listing of internal hubs is A>Z by manufacturer, then by number of speeds, type and age.
Fichtel & Sachs, Sachs and SRAM are the same series of hubs, shown together.
This page covers most internal hubs back to the original 1902 Sturmey-Archer.
Many internal-gear hubs listed and some of the cassettes are no longer in production.
Clicking on "calculate" generates two new output pages: a full-size one, and a small one which you might print out and tape to your bicycle's handlebar stem for reference. The small one will overlay the large one in a browser which supports tabs.
If you do a calculation, then bring those to the front, subsequent "results" windows from subsequent calculations may be hidden behind them.
For multiple calculations, you should close each set of results in turn, not hide them.
The selection of internal-gear hubs in the Calculator is complete except for one a few new models whose gear ratios have not been made public, and some very rare antiques. The selection of cassettes is up to date as of February 2018 for Shimano, SRAM, SunRace and recent Campagnolo models. For brands and models not covered, or if building up a custom cassette, you will need to count sprocket teeth and enter the tooth counts under "custom sprockets." Our cassette page links to additional information on cassette tooth counts.
If you're using a Schlumpf Drive plus an internal-gear rear hub you should enter the actual number of teeth of the front chainring for the first chainring, and this number of teeth times the Schlumpf ratio for the second chainring. The ratios are 0.40 for the Mountain Drive, 1.65 for the Speed Drive, and 2.50 for the High Speed Drive.
Peter Heinle has an Excel spreadsheet online with the tooth counts of a large number of 10-through 13-speed cassettes
The SRAM/Sachs 3 x 7, 3 x 8, 3 x 9, 3 x 10 and the Sturmey-Archer CS- RF3 and CS-RK3
are the only recent/current production internal-gear hubs designed to use rear sprocket clusters;
The Sturmey-Archer-Brompton BWR takes two sprockets,
but other models are included in the list for the benefit of tinkerers -- see discussion.
Gain Ratios |
Gear Inches |
Meters Development |
About Percentages |
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If you do a calculation, get a result, then bring this window to the front, subsequent "results" windows from subsequent calculations may be hidden behind this window.
For multiple calculations, you should close each "results" window in turn, not hide them.