I know app developers submit square icons and Apple does the actual rounding. But for comps. and other presentations, as well as setting up icon inner shadows and glows, etc., it is vital to know the EXACT corner rounding ratio...
http://www.cultofmac.com/231487/jon...s-icons-the-same-rounded-corners-as-the-imac/
http://www.cultofmac.com/231487/jon...s-icons-the-same-rounded-corners-as-the-imac/