Erect length
Standing, hold your erection horizontal. Hold the ruler to the base but DO NOT press the ruler into the fat pad which is against your pubic bone. Get an honest measurement on top of the penis to the tip of the head/glans.
Erect Girth
With a piece of string or cloth measuring tape, measure the circumference of your erect penis at the thickest part of the shaft. If you want to do better take three measurements at the base, middle and just on or just behind the head rim.
Flaccid maximum, minimum, average
Measure yourself many times to get a good idea where you're starting from. Try lying on your back to measure the minimum.
Visual comparisons
Compare yourself in the mirror with some object that will be around a few months from now - a toilet paper tube or deodorant container. These visual comparisons are much more powerful than simply using numbers.
Measuring the penis
To get the most accurate measurements for an individual's penis size, it has been recommended that several measurements be taken at different times, preferably with different erections on different days. The measurements are then to be averaged together.
This is to account for what may be natural variability in size due to factors such as arousal level, time of day, room temperature, frequency of sexual activity, and unreliability of the measurement methods.
Length
The length can be measured with the subject standing and the penis held parallel to the floor. The penis is measured along the top, from the base to the tip. Results are inaccurate if the measurement is taken along the underside of the penis, or if the subject is seated or prone.
Circumference
Penis girth is the measurement of the circumference of the completely erect penis. It is variously quoted as an average of three measurements: just below the glans penis, in the middle of the shaft, and at the base.
Problems
A penis must be completely erect in order to obtain an accurate measurement. This may be difficult to achieve in a clinical setting. At least one Brazilian doctor resorted to
injecting penises with drugs to induce erection, which gave more consistent results. Some clinicians measure the penis by stretching the flaccid penis as far as comfortably possible.
Studies on penis size
While results vary across studies, the consensus is that the mean human penis is approximately 12.9–15 cm (5.1–5.9 in) in length with a 95% confidence interval of (10.7 cm, 19.1 cm) (or, equivalently, 4.23 in, 7.53 in).
The typical girth or circumference is approximately 12.3 cm (4.85 in) when fully erect.
The mean penis size is slightly greater than the median size. Contrary to popular belief, there is no scientific relation between penis size and race.
Human penis size
Comparison of two circumcised human penises, erect (on left) and flaccid (on right).
Human penis size refers to the length and width of human male genitalia.
Penis size changes with aging
Age is not believed to negatively correlate with penis size. “Individual research studies have… suggested that penis size is smaller in studies focusing on older men, but Wylie and Eardley found no overall differences when they collated the results of various studies [over a 60 year period].”
Erect length
Several scientific studies have been performed on the erect length of the adult penis.
Studies which have relied on self-measurement, including those from Internet surveys,
consistently reported a higher average length than those which used medical or scientific methods to obtain measurements.
The following staff-measured studies are each composed of different subgroups of the human population (i.e. specific age range and/or race; selection of those with sexual medical concerns or self-selection) which could cause a sample bias.
• A study published in the September 1996 Journal of Urology concluded that average erect length was 12.9 cm (5.08 in) (measured by staff). The purpose of the study was to “provide guidelines of penile length and circumference to assist in counseling patients considering penile augmentation.” Erection was pharmacologically induced in 80 physically normal American men (varying ethnicity, average age 54). It was concluded:
“Neither patient age nor size of the flaccid penis accurately predicted erectile length.”
• A study published in the December 2000 International Journal of Impotence Research found that average erect penis length in 50 Jewish Caucasian males was 13.6 cm (5.35 in) (measured by staff)] Quote: "The aim of this prospective study was to identify clinical and engineering parameters of the flaccid penis for prediction of penile size during erection." Erection was pharmacologically induced in 50 Jewish Caucasian patients who had been evaluated for erectile dysfunction (average age 47±14y). Patients with penis abnormalities or whose ED could be attributed to more than one psychological origin were omitted from the study.
• A study conducted by LifeStyles Condoms found an average of 14.9 cm (5.9 in) with a standard deviation of 2.1 cm (0.8 in) (measured by staff). The purpose of this study was to ensure properly sized condoms were available.
• A review published in 2007 issue of BJU International, have shown that average erect penis length is 14–16 cm and its girth is 12–13 cm. This paper compares results of twelve studies conducted on different populations in several countries.
• An Italian study of about 3,300 Italian men concluded that stretched length was measured on average to about 5 inches. In addition, a correlation between weight and height and penis length was also found. However this was done only on 500 men with a small correlation value.
Erect circumference
• The Cancún LifeStyle study, in which the circumference of the shaft was measured at three points (base, mid-shaft, and just below the head) and then averaged, found an average of 12.63 cm (4.972 inches) with a standard deviation of 1.3 cm (0.5 in).
Similar results exist regarding studies of the circumference of the adult fully erect penis, with the measurement taken mid-shaft.] As with length, studies that relied on self-measurement consistently reported a significantly higher average than those with staff measuring.
Flaccid Length
One study found the mean flaccid penis length to be 3.5 inches (8.9 cm) (measured by staff). A review of several studies have shown average flaccid length to be 9–
10 cm. Length of the flaccid penis does not necessarily correspond to length of the erect penis; some smaller flaccid penises can grow much larger, and some larger flaccid penises cannot grow much larger.
The penis and scrotum can contract involuntarily in reaction to cold
temperatures or nervousness, referred to by the slang term "shrinkage", due to action by the cremaster muscle. The same issue affects cyclist and exercise bike users, with prolonged pressure on the perineum from the saddle, and the straining of the exercise causing the penis and scrotum to contract
involuntarily which is sometimes referred to as "gym balls" or "saddle balls". An
incorrect saddle may ultimately cause erectile dysfunction (see crotch pressure for more information).
Penises that are short when flaccid but more average when erect are colloquially known as growers, where those with greater flaccid lengths that increase little when erect are known as showers.
Flaccid penis length is a poor estimate of erect length, a better estimate is stretched length, that is 12–13 cm, as shown in review by Wylie and Erdley.