Exact Border Radius for iOS Icons

Great answer by David Barnard on a question over at Stackoverflow:

Apple starts with the 57px icon and a radius of 10 then scales up or down from there. Thus you can calculate the radius for any icon size using 10/57 x new size (for example 10/57 x 114 gives 20, which is the proper radius for a 114px icon).

And for the lazy ones, he listed the calculations for the most common icons:

Published in | 25 Apr 2012