scientists who reviewed 20 different studies of penis size , including 15,521 measurements of penises from around the world .
most men fall within just a couple of centimetres of each other , with most measuring around 5.2 inches in length when erect with a 4.6 inch circumference .
if he wants to diy , the correct way to measure a penis is to use a cloth measuring tape , not a straight-edged ruler that