I'm not sure that it is in the standards. You may want to ask over on forum1103.
I couldn't see it in ASME Y14.5M-1994. B4 does give the equations for calculating position tolerance from the sizes of the male/female components.
The equation you give is for converting +- coordinate dims to position, instead 14.5 concentrates on determining the pos tol from true function, hence B4.
KENAT,
Have you reminded yourself of faq731-376 recently, or taken a look at posting policies: