What is the Normal Penis Size by Age?
Medically reviewed by Andre Stone | MD, University of Pittsburgh School of Medicine on August 25th, 2026.
Normal penis size varies significantly throughout development, with adult length averaging 5.16 inches when erect. Average stretched penis length is about 1.4 inches in full-term newborns and generally increases during childhood. Estimates at specific ages vary among studies and populations. Penis growth usually increases during puberty, but the timing varies. Development may begin earlier or later and can continue into late adolescence. In a large systematic review, average adult length was about 3.6 inches when flaccid and 5.2 inches when erect. Individual measurements vary widely. The adult averages come from a systematic review of measurements taken by health professionals in more than 15,000 men. The childhood estimates come from separate pediatric studies. Significant variation exists within normal ranges.
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