I'm not sure how it would work using the typical O gauge nomenclature (O-27, O-31, etc.), but in other scales that use the frog number to identify the switch, a number 6 turnout's radius is half the radius used for a number 6 Wye, since both legs are curved in a Wye, while only one is curved in a turnout, but the diveraging angle is the same.
Bill in FtL