Let’s talk about the size of the foreskin. Anti-circumcision activists, called “intactivists,” like to say that the adult foreskin is about 15 square inches and so it makes up over 50% of the skin on the penis. This is really, frankly, irrelevant information if circumcision does not harm sexual or penile function, which it does not. If circumcision has no sexual or functional harms, then how much skin is removed is irrelevant. Nonetheless, it’s yet another claim that intactivists make, and so we’re going to look at it in some detail.
How Big is the Penis?
First off, what is the length of the penis? After all, if we want to know how much of the penis skin is foreskin, we need to know how long the penis is. A systematic review of all studies on the subject published in 2015 found that among 15,521 men across the planet, the average length of the penis is 9.16 cm flaccid and 13.12 cm erect (Veal et al, 2015).
Only less than 2.5% of men have a penis shorter than 10 cm erect and only 5% of men have a penis longer than 16 cm erect (Veal et al, 2015). This means that about 92.5% of men have a penis that ranges 3.9 to 6.3 inches, or about 4 to 6 inches long erect. There’s not much variation there, the shortest normal length varying only about 33% from the maximum normal length. The normal, non-prolapsed vagina is 10-12 cm (3.9-4.7 in) long (Matthes & Zucca-Matthes, 2016). So, in other words, the average erect penis is longer than the average vagina. This may be why the penis varies as much as it does but not more than that. Because the only evolutionary or created advantage to penis length would be a penis that is just long enough to deposit sperm near the cervix.
Flaccid, the difference in length is more pronounced. For example, only 2.5% of men have a flaccid penis shorter than 6 cm and almost 5% of men have a flaccid penis longer than 12 cm (Veal et al, 2015). This means for about 92.5% of men, the flaccid length is within 6-12 cm or 2.4-4.7 inches, almost 2.5 to 5 inches. In other words, the flaccid length differs much more than the erect length, as much as 50% of the maximum normal length. This should not come as a surprise, however, because the flaccid length is irrelevant to reproduction. Even though flaccid length varies significantly, erect length does not, and the erect length is what matters for reproduction.
The circumference of the penis, which is how big around it is, averages 9.31 cm flaccid and 11.66 cm erect. About 7.5% of men have a flaccid circumference less than 8 cm and about 2.5% have a flaccid circumference greater than 11 cm (Veal et al, 2015). So about 90% of men have a circumference that ranges 8-11 cm or 3.1-4.3 inches. Again, not a whole lot of variation there, only 28% from the max normal circumference.
How Big is the Foreskin?
In contrast, there is vast variation in the size of the foreskin. One study of almost 1,000 men (Kigozi et al, 2009) found that the inner and outer foreskin together averaged 35.0 cm2 (5.4 in2) and ranged in size from 7 cm2 (1.1 in2) to 99.8 cm2 (15.5 in2). If the average circumference, as we discussed already, is 9.3 cm, and the foreskin’s area measures 7-99.8 cm2, that means the foreskins were on average 3.8 cm (1.5 in) long and ranged anywhere from 0.75 cm (0.3 in) to 10.7 cm (4.2 in) long, including outer and inner foreskin. About 6.3% of men (the top 25% of the top 25%) had foreskins larger than 61.8 cm2 (9.6 in2) and about 6.3% (the bottom 25% of the bottom 25%) had foreskins smaller than 18.0 cm2 (2.8 in2) (Kigozi et al, 2009). So for almost 90% of men, the foreskin ranges in size from 2.8 in2 to 9.6 in2. Again, assuming the average circumference is 9.3 cm, this means the length (inner and outer foreskin combined) ranges 1.9 cm (0.76 in) to 6.6 cm (2.6 in), meaning the shortest normal length varies 71% from the longest normal length. This is a vast difference compared to the differences in penis length and penis circumference, which varies about 33% and 28%—i.e., less than half as much as the length of the foreskin.
What Proportion of the Skin is Foreskin?
If we just take the simple averages of the length of the penis (9.3 cm flaccid) and the length of the foreskin (3.8 cm), the foreskin makes up 29% of the skin of the penis. This is obviously much less than the intactivist claim of 50%.
If we assume that the shortest penises had the shortest foreskins and the longest penises had the longest foreskins:
- The shortest normal size (6 cm flaccid penile length and 0.75 cm length of inner and outer foreskin) accounted for 11% of the skin of the penis.
- The longest (12 cm flaccid penile length and 6.6 cm length of inner and outer foreskin) accounted for 35% of the skin of the penis.
If we assume the reverse, that the longest penises (12 cm flaccid) had the shortest foreskins (0.75 cm inner and outer), the foreskin would account for 6% of the skin of the penis. If we assume that the shortest penises (6 cm flaccid) had the longest foreskins (6.6 cm inner and outer), the foreskin would account for 52% of the skin of the penis.
In other words, it is only by making the most extreme comparison that we can finally get the number over 50% (or, on the other extreme, only 6%), in accordance with intactivist claims that the foreskin makes up 50% or more of the skin of the penis. (I’ve even seen the claim that it makes up 80%!) Most likely, the foreskin makes up less than a third of the skin of the penis. Until further research demonstrates this to be false, I think this is as accurate as it gets. Although once again, it’s irrelevant if circumcision does not harm sexual or penile function, and we know that it does not.
As a final note, recall that we found the length of the penis does not vary much in comparison to the length of the foreskin. An acquaintance of mine, writing previously on the topic of foreskin size, quoted Darwin (though I think it equally true of creation):
“An organ, when rendered useless, may well be variable, for its variations cannot be checked by natural selection.”
In short, the wildly variable length of the foreskin compared to the much less variable length and girth of the penis indicates that the foreskin is of little importance anymore. Presumably it was before the Flood radically changed the global environment (if you’re a creationist) or back when we were essentially apes (if you’re an evolutionist), but modern evidence indicates that it is of little importance now.
Kigozi, G., Wawer, M., Ssettuba, A., Kagaayi, J., Nalugoda, F., Watya, S., … & Serwadda, D. (2009). Foreskin surface area and HIV acquisition in Rakai, Uganda (size matters). AIDS (London, England), 23(16), 2209. doi: 10.1097/QAD.0b013e328330eda8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3125976/
Matthes, A. C. S., & Zucca-Matthes, G. (2016). Measurement of vaginal flexibility and its involvement in the sexual health of women. Journal of Women’s Health Care, 5(1), 1-4. doi: 10.4172/2167-0420.1000302. https://www.researchgate.net/profile/Angelo_Matthes/publication/298805584_Measurement_of_Vaginal_Flexibility_and_Its_Involvement_in_the_Sexual_Health_of_Women/links/5729e72b08ae2efbfdbbfbd5.pdf
Veal, D., Miles, S., Bramley, S., Muir, G., & Hodsoll, J. (2015). Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15,521 men. BJU International, 115(6), 978-986. doi: 10.1111/bju.13010. http://onlinelibrary.wiley.com/doi/10.1111/bju.13010/full