A reader submitted the following question:

"How deep is a typical vagina? I hear a lot about penis size, but what about vagina size? Does size vary across nations?"

Thanks for these great questions! You're absolutely right that vaginal size is a topic that hasn't been discussed or researched nearly as often as penis size; however, there is some data out there that can speak to your questions.

Sex researchers William Masters and Virginia Johnson were among the first to scientifically study vaginal dimensions, which they reported on in their classic 1966 book Human Sexual Response (a copy of which I keep on my shelf) [1]. As noted on page 74 of this book, they took measurements of the "vaginal barrels" of 100 nulliparous women (i.e., women who had never before given birth). On a side note, I've never heard anyone other than Masters and Johnson use the term "vaginal barrels" before--but, then again, they were famous for using very dry, clinical language in their work because they were afraid of their research coming across as pornographic in those days.

Masters and Johnson reported that vaginal length ranged from 7-8 cm (2.8-3.1 inches) in a sexually unaroused state, but increased to 9.5-10.5 cm (3.7-4.1 inches) during sexual arousal. The length was even longer (11-12 cm or 4.3-4.7 inches) when measured during sexual arousal with a vaginal speculum in place. Thus, the depth of the vagina (just like the length of the penis) appears to increase significantly when aroused.

A more recent study published in the 1990s found even greater variability in vaginal depth [2]. This study involved 39 White women (one-third of whom had never given birth before), and revealed that vaginal lengths ranged from 6.9-14.8 cm (2.7-5.8 inches). These measurements were obtained by taking vinyl polysiloxane casts of the vagina.

I'm not aware of any research that has compared vaginal dimensions cross-culturally; however, the researchers I just mentioned who made vaginal casts of White women conducted a follow-up study a few years later in which they made vaginal casts of women of different races (African American, White, and Hispanic) [3]. They obtained evidence of some variation in vaginal dimensions across racial groups; however, the sample sizes were very small (only 23 African American and 15 Hispanic women participated). Thus, while the results suggested the possibility that (just like penis size) there may be differences in vaginal size across races, more research is needed before drawing any firm conclusions.

One final thing worth noting is that when you compare these vaginal depth measurements to the average penis length, you'll see that the average vaginal depth appears to be a little shorter than the average penis length. Perhaps that's why researchers have found that most heterosexual women do not necessarily think that longer is better when it comes to penis size.

For past Sex Question Friday posts, see here.

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[1] Masters, W. H., & Johnson, V. E. (1966). Human sexual response. Boston, MA: Little, Brown.

[2] Pendergrass, P. B., Reeves, C. A., Belovicz, M. W., Molter, D. J., & White, J. H. (1996). The shape and dimensions of the human vagina as seen in three-dimensional vinyl polysiloxane casts. Gynecologic and Obstetric Investigation, 42(3), 178-182.

[3] Pendergrass, P. B., Reeves, C. A., Belovicz, M. W., Molter, D. J., & White, J. H. (2000). Comparison of vaginal shapes in Afro-American, Caucasian and Hispanic women as seen with vinyl polysiloxane casting. Gynecologic and Obstetric Investigation, 50(1), 54-59.

Image Source: 123rf.com/lculig

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