Ranges of Medically Acceptable Infant Clitoral and Penile Lengths
In Suzanne Kessler's research of the intersexed, she finds that physicians use size to determine sex assignment of intersexed infants. Clitorises with the length of 0.2-0.9cm and penises with the length of 2.5-4.5cm are considered medically acceptable. Genitals within the range of 0.9-2.5 are considered unacceptable. Boys with penises smaller than 2.5 cm may be reassigned as girls.
--from The Five Sexes, Revisited