How common is erect girth of 13.5 cm
Executive summary
An erect penile circumference (girth) of 13.5 cm is modestly above published global averages and, based on clinician‑measured sample means and reported standard deviations, would place a man roughly around the 60th–70th percentile — meaning about one‑third of men would have equal or greater girth — but that figure depends on which study and population one uses and is sensitive to measurement methods [1] [2] [3] [4].
1. What the major reviews report about “average” erect girth
Large systematic reviews and clinician‑measured datasets repeatedly place average erect girth in the neighborhood of 11.6–12.3 cm: a widely cited 2015 clinician‑measured meta‑analysis reported an average erect circumference of 11.66 cm (4.59 in) [1] [2], while individual physician‑measured studies have reported means of 12.3 cm (SD 2.9) in one series [3] and 12.03 cm (SD 3.82) in a large Italian clinical sample [4]; these are the best available anchors for assessing how common 13.5 cm is across clinical samples [1] [2] [3] [4].
2. Translating a raw measurement into a prevalence estimate
Using the clinician‑measured study means and their reported standard deviations as a working model, 13.5 cm is about 0.38–0.41 standard deviations above those means, which corresponds to roughly the 65th–66th percentile of a normal distribution — i.e., around 34–35% of men would have an erect girth equal to or greater than 13.5 cm in those datasets (calculation using mean 12.3 cm, SD 2.9 and mean 12.03 cm, SD 3.82) [3] [4]. If one instead anchors to the pooled mean of 11.66 cm without a reported SD in the same source, the percentile shifts upward (13.5 becomes even more above mean), but the precise prevalence cannot be determined without an SD from that pooled analysis [1] [2].
3. Important caveats: measurement methods and heterogeneity
Published penile‑size literature varies by whether measurements were clinician‑taken or self‑reported, by how “erection” was induced or defined, and by where girth was measured on the shaft; studies that used self‑measurement tend to report larger averages than clinician measurement, and different studies report different standard deviations, so simple percentile math can give a misleading sense of precision if those methodological differences aren’t considered [1] [2] [3]. Meta‑analysts warn about publication and selection biases and heterogeneity between regions and study protocols, and note that including all studies without exclusion may mask underlying biases in pooled estimates [5].
4. Population variation and representativeness
Some large national or regional clinical cohorts show slightly higher means (for example, the Italian clinical series reported mean erect girth ~12.03 cm), whereas pooled meta‑analyses across continents report the 11.66–11.7 cm global average; neither set is a perfect representation of every country or demographic, and differences within regions often exceed differences between regions, so prevalence estimates for a specific country or age group may differ from the global ballpark used here [4] [5] [2].
5. Bottom line and practical interpretation
An erect girth of 13.5 cm is above the commonly reported global mean and should be regarded as larger than average but not rare — using clinician‑measured study parameters it sits near the upper third of the distribution so roughly one in three men could measure at or above that girth in those clinical samples [3] [4]. Because measurement technique, sample selection, and reporting practices materially change point estimates, any precise percentile should be reported with the study and method used to produce it rather than offered as a single universal truth [1] [2] [5].