The sprocket ratio on the Rohloff SPEEDHUB 500/14 (e.g. 42/16) converts the slow rotational speed at the crank into a fast rotational speed at the sprocket and reduces the input torque for the Rohloff SPEEDHUB 500/14 in the same proportion. To prevent overstraining the hub, a minimum sprocket ratio of 1.9 must be used. With the available sprockets these minimum ratios are achieved by: 40:21, 32:17, 30:16, 28:15 and 26:13. This resembles a derailleur transmission of 20:40. Larger chainrings can be used without exceptions. 

If mounted on a tandem or if the rider weighs over 100kg, the following sprocket ratios must not be undercut: 34:13, 38:15, 40:16, 42:17 and 53:21. 

The sprocket and chainring calculator on this page is made by Dirk Feeken from "www.ritzelrechner.de". 
We appreciate the effort and permission to use this usefull online tool on our web pages.