If your mate's trying to claim he's housing a large package off the back of his shoe size, it's time to call him out.
After observing 104 patients at the London urology clinic, including men of all ages, researchers measured the length of a flaccid penis when stretched.
"All lengths were measured by two urologists and recorded to the nearest 0.5cm. The age and shoe size was documented," wrote the researchers.
Results found the average penis length was 13cm when flaccid and stretched - the largest being 18cm, the smallest, 6cm.
The average shoe size was 43EU. Scientists couldn't draw a correlation between between the two sizes.
"Many believe that the size of a man's penis can be estimated by assessing various other parts of his body, notoriously his shoe size," continues the study.
""The ability to predict the size of a man's penis by observing his shoe size is a common misconception.
"The present study shows that there is no scientific support for the relationship."
Interestingly, a study in Korea found there to be a link between finger length and penis size.
Gathering 144 men aged over 20 and undergoing urological surgery, researchers from Gachon University measured the length of both the index and ring fingers before determining the size of their willies.
Remarkably, results showed that if there was a substantial difference between a man's index and ring finger, there's a good chance he was packing some serious heat.
Be right back... have to quickly measure my fingers. Bet you're doing the same?