Average White penile length: 5.6-5.7 inches.
-Department of Urology, University of Essen, Germany: http://www.ncbi.nlm.nih.gov/pubmed/11182344
Average Black penile length: 5.3 inches.
-Department of Surgery, Nnamdi Azikiwe University, Nigeria: http://www.ncbi.nlm.nih.gov/pubmed/17191423?dopt=AbstractPlus
This is the only study conducted on black penile length that is not self reported, but measured in a lab.