Depends which authority you want to know it for.
For the FAA there is no standard for a class 3 medical.
For classes 1 and 2:
Hyperphoria: 1 Diopter
Eso/Exophoria: 6 Diopters
Maddox rod is a oblong approximately 1 x 6 inch piece of (?glass or other transparancy) with a gradation of prisms.
It is used togethere with a light. The subject (that is you!) must align a light with the line seen through the glass. The amount of diopters needed to align the two is a measure of phoria.
HTH
FD
PS: Forgot to write that any decent optician/eyeclinic can measure this