The average erect penis girth is about 11.66 cm, or roughly 4.6 inches, measured around the thickest part of the shaft. When flaccid, the average circumference drops to about 9.31 cm (3.7 inches). These figures come from a widely cited meta-analysis of over 15,500 men published in BJU International, and they’ve held up well in newer research.
What the Largest Studies Found
The most referenced dataset on penis dimensions was compiled in 2015 by researchers at King’s College London, who pooled measurements from 15,521 men across multiple studies. For erect girth specifically, the mean was 11.66 cm with a standard deviation of 1.10 cm. That standard deviation means roughly two-thirds of men fall between about 10.5 cm (4.1 inches) and 12.8 cm (5.0 inches) when erect.
A more recent meta-analysis published in 2025 examined 36,883 men across 33 studies and found very similar results: a mean erect circumference of 11.91 cm (4.7 inches) and a mean flaccid circumference of 9.10 cm (3.6 inches). The slight difference between the two analyses isn’t meaningful. Both point to the same ballpark. Regional variation exists, with men in the Americas showing a slightly higher average flaccid girth of about 10.0 cm, though sample sizes across regions weren’t equal.
How Girth Is Measured
In clinical studies, girth is measured by wrapping a flexible tape around the thickest part of the shaft, usually just below the head. If you’re measuring at home, a soft measuring tape works best. Wrap it snugly but not tightly around the widest point, and read where the tape meets itself. No measuring tape? Wrap a piece of string, pinch where it overlaps, and lay the string flat against a ruler.
A few things can throw off your measurement. Cold temperatures cause temporary shrinkage, so a warm room gives a more representative result. Some fabric measuring tapes stretch slightly when pulled, which can inflate the number. And because girth can vary along the shaft, measuring at the thickest point is the standard method used in research.
Why Girth Varies Less Than You’d Expect
Compared to length, girth tends to cluster more tightly around the average. The standard deviation for erect length is larger relative to its mean, meaning there’s more person-to-person variation in how long a penis is than in how thick it is. Most men are within about half an inch of the average girth in either direction.
There’s no strong evidence that girth correlates with height, shoe size, or body mass index. Girth does tend to increase somewhat alongside length, meaning longer penises are often slightly wider, but the relationship is modest. In one modeling study, an 8 cm increase in length corresponded to only about a 1.2 cm increase in width.
What Girth Means for Condom Fit
Girth is actually more important than length when choosing a condom. Most condoms are sold with a “nominal width,” which is the width of the condom when laid flat. To find yours, divide your circumference by 3.14 to get your diameter, then divide that by two for the flat width. For someone right at the 11.66 cm average, that works out to a flat width of about 1.85 cm, or roughly 53 mm, which fits standard-sized condoms from most brands.
A condom that’s too narrow for your girth will feel uncomfortably tight and is more likely to break. One that’s too wide may slip during use, reducing both effectiveness and sensation. If standard sizes feel consistently wrong in either direction, snug-fit and larger options are widely available and sized specifically around circumference rather than length.
Perception vs. Reality
Studies consistently find that men overestimate how large the “average” penis is, largely because the most visible reference points (pornography, exaggerated self-reporting in surveys) skew perception upward. In the 2015 King’s College analysis, the researchers noted that self-reported measurements ran noticeably higher than clinician-measured ones, which is why the most reliable data comes from studies where a healthcare professional took the measurement.
If your erect girth falls anywhere between about 4 and 5 inches, you’re squarely within the normal range that accounts for the vast majority of men. Even measurements a bit outside that window are not unusual given natural human variation.