Penis size FAQ and bibliography

The answers to the following questions are based on original research data collected by Dr. Alfred Kinsey and his research team.

Q. What is the range of erect penis length for most men?
A. 5–6.5 inches*

Q. What is the average circumference?
A. 4–5 inches*

* Gebhard and Johnson, 1979, p. 120

How did the Kinsey researchers measure penis size?

Men were asked: "How long is your penis, measuring on the top side from your belly out to the tip?" They were each given a pre-stamped card to take home, and instructed to mark the length on the card when flaccid and when erect. Approximately 2,500 men participated.

During interviews with over 4,000 men, the interviewer asked each subject to estimate his penis size. The interviewer would hold out a ruler (the numerals were not visible to the subject) and move his finger along it.

There was a slight underestimation of penis size compared with actual measurements.
(Gebhard & Johnson 1979, p. 116.)

What is the relationship between the size of a flaccid (soft) penis and an erect (hard) penis?

There is a much wider range of size in men's penises when flaccid, with the average ranging from 1 to 4 inches. In general, smaller, flaccid penises lengthen at erection by a greater percentage than larger, flaccid penises, with most men reaching an average size of 5 to 7 inches. This means the flaccid size of a penis is not a good predictor of erect size. The vast majority of men measure within the average genital size range and have a penis size that is more than adequate for sexual functioning.

What is a micropenis?

This term is used by researchers to refer to penises less than 2.8 inches (7 centimeters) in length when stretched. This condition is thought to affect only 0.6% of men (or six in 1,000 men) and caused by inadequate testosterone at a late stage of fetal development.

Can you make a penis bigger in length or girth?

There is no non-surgical technique to make the penis bigger. Penis pumps may help create a stronger erection, but they will not create a larger penis.  Because the penis is composed largely of spongy erectile tissue and not of muscle, it cannot be strengthened or "built up." Surgery may cause scar tissue to grow that can cause a painful or even a shortened erection.

Penis Size Bibliography

Below is a selected bibliography of research resources related to penis size compiled in response to frequent questions received by the Institute.

For a review of penis size studies, see Wylie, K.and Eardley, I. Penile Size and the 'Small Penis Syndrome.' BJU International, 99(6) 1449-1455

  • Alter, G.J. (1995). Augmentation phalloplasty. Urologic Clinics of North America, 22(4), 887-902. 
  • Alter, G.J. (1998). Penile enlargement surgery. Techniques in Urology, 4(2), 10-76.
  • Alter, G.J. (1997). Reconstruction of deformities resulting from penile enlargement surgery. Journal of Urology, 158(6), 2153-7.
  • Bogaert, A.F., and Hershberger, S. (1999) The relation between sexual orienation and penile size. Archives of Sexual Behavior, 28(3), 213-221.
  • da Ros, C., et al. (1994). Caucasian penis: What is the normal size? Journal of Urology, part 2, 151: 323A, abstract 381.
  • Fisher, William A., Branscombe, Nyla R., and Lemery, Charles R. (1983). The bigger the better? Arousal and attributional responses to erotic stimuli that depict different size penises. Journal of Sex Research, 19(4), 377-396.
  • Furr, Karl D. (1991). Penis size and magnitude of erectile change as spurious factors in estimating sexual arousal. Annals of Sex Research 4(3/4), 265-279.
  • Gebhard, Paul, and Johnson, Alan. (1979/1998). The Kinsey Data: Marginal Tabulations of the 1938-1963 Interviews Conducted by the Institute for Sex Research (reprint edition). Bloomington, IN: Indiana University Press. 
  • Gilbaugh, James H. (1989). A Doctor's Guide to Men's Private Parts. New York : Crown Publishers.
  • de Groot, Erik R., Spiering, Mark, Both, Stephanie, de Bruijn, Wouter, Gritter, Bettine, and Rommens, Paul. (2006). Het formaat van de panis: Was will der Mensch? Tijdschrift voor Seksuologie 30, 150-159.
  • Jamison, P.L., and Gebhard, P.G. (1988). Penis size increase between flaccid and erect states: An analysis of the Kinsey data. Journal of Sex Research, 24, 177-183.
  • Janssen, Erick. (1994). Penile circumference variability in a Dutch sample. Amsterdam,
  • The Netherlands: Condomerie.
  • Johnston, J. H. (1974). Lengthening of the congenital or acquired short penis. British Journal of Urology, 46(6), 685-8.
  • Jung-Ho Han, Sang-Hwa Park, Bong-Sam Lee and San-Un Choi(1999). Erect penile size of Korean men. Venereology 12(4), 135-139.
  • Lee, P. A., Mazur, T., Danish, R., Amrhein, J., Blizzard, R. M., Money, J. and Migeon, C. J. (1980). Micropenis. I. Criteria, etiologies and classification. Johns Hopkins Medical Journal, 146:156.
  • Lee, Peter A. (1996). Survey report: Concept of penis size. Journal of Sex & Marital Therapy, 22(2), 131-135.
  • Long DC. [Elongation of the penis]. [Chinese]. (1990). Chung-Hua Cheng Hsing Shao Shang Wai Ko Tsa Chih - Chinese Journal of Plastic Surgery & Burns, 6(1),17-9, 74.
  • Masters, W. H., and Johnson, V. E. (1966). Human Sexual Response. Boston: Little, Brown & Co.
  • Money, John, et al. (1984). Micropenis: Adult follow-up and comparison of size against new norms. Journal of Sex & Marital Therapy, 10(2), 105-114.
  • Phillip, M., et al. (1996). Clitoral and penile sizes of full term newborns in two different ethnic groups. Journal of Pediatric Endocrinology & Metabolism, 9(2), 175-9.
  • Pietropinto, Anthony.(1986). Misconceptions about male sexuality. Medical Aspects of Human Sexuality, 20(11), 80-85.
  • Reilly, J.M., and Woodhouse, C.R.(1989). Small penis and the male sexual role. Journal of Urology, 142(2 Pt 2), 569-71, discussion 572.
  • Schonfeld, W. A. (1943). Primary and secondary sexual characteristics: Study of their development in males from birth through maturity, with biometric study of penis and testes. American Journal of Diseases of Children, 65, 535.
  • Schonfeld, W. A. and Beebe, G. W. (1942). Normal growth and variation in the male genitalia from birth to maturity. Journal of Urology, 48, 759.
  • Siminoski, Kerry. (1993). The relationship among height, penile length, and foot size. Annals of Sex Research, 6(3), 231-235. 
  • Smith, D.P., Rickman C., and Jerkins, G.R. (1995). Ultrasound evaluation of normal penile (corporeal) length in children. Journal of Urology, 154(2 Pt 2), 822-4.
  • Sparling, Joseph. (1997). Penile erections: Shape, angle, and length. Journal of Sex & Marital Therapy, 23(3), 195-207.
  • Stock, J.A., Packer, M.G., and Kaplan, G.W. (1995). Pediatric urology facts and figures. Data useful in the management of pediatric urologic patients. Urologic Clinics of North America, 22(1),205-19.
  • Tenzer, Lawrence R. (1990). A Completely New Look at Interracial Sexuality: Public opinion and Select Commentaries. Manahawkin, N.J.: Scholars' Pub. House, 1990.
  • Wessells, H., Lue T.F., and McAninch, J.W. (1996). Complications of penile lengthening and augmentation seen at 1 referral center. Journal of Urology, 155(5), 1617-20.
  • Wessells, H., Lue, T.F., and McAninch, J.W. (1996). Penile length in the flaccid and erect states: Guidelines for penile augmentation. Journal of Urology, 156(3), 995-7. 
  • [Data from 80 subjects; mean flaccid length was 8.85 cm. and mean erect length was 12.89 cm. The difference between these 2 dimensions was considered the erectile increase (mean 4.04 cm.).]
  • Winter, Harold C. (1989). An examination of the relationships between penis size and body image, genital image, and perception of sexual competency in the male. Dissertation Abstracts International, 50(5-A), 1225
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