What is the average erect penis girth and how does it scale with length?
Executive summary
Measured-by-clinician studies put average erect circumference (girth) at about 11.66 cm (4.59 in) and average erect length near 13.12 cm (5.17 in); these figures come from a large 2015 systematic review that consolidated clinician-measured data up to that point [1]. Multiple health and science outlets cite the same review and report that girth clusters near 11.7 cm while erect length clusters near 13.1 cm, and self-reports tend to be higher than clinician measurements [2] [1] [3].
1. What the best-measured surveys say: a short, hard number
The most-cited clinician-measured synthesis (a systematic review used by Wikipedia and others) found an average erect circumference of 11.66 cm (4.59 in) and an average erect length of 13.12 cm (5.17 in) [1]. Several patient-facing sites and professional organizations repeat those numbers, noting the data set covered thousands of men measured by health professionals rather than self-report [3] [4].
2. Why clinician-measured and self-reported figures differ
Self-reports routinely yield larger averages—examples in secondary sources list self-reported erect length near 5.6 in and girth near 4.8 in—because of measurement method, selection bias and reporting bias [5]. The 2015 review explicitly distinguishes staff-measured results from self-measured studies; studies measured by professionals give lower, more consistent averages [1].
3. How girth scales with length: what the sources do and don’t say
Available sources report separate averages for erect length and for erect circumference but do not present a definitive, universal scaling law that links an individual’s length to their girth. The systematic review gives population means—erect length ≈13.12 cm and erect girth ≈11.66 cm—but does not claim a precise one-to-one scaling formula [1]. Other sources note weak correlations between flaccid and erect measures, and that individual variation is substantial [6] [3]. In short, population averages are clear; the exact way girth scales with length for any given man is not specified in the cited reporting [1] [6].
4. Distribution and percentiles: most men fall into a mid-range
The aggregated evidence indicates most erect lengths lie roughly between about 10–16 cm (3.9–6.3 in) for roughly 85% of men, with girth clustering near the mean of ~11.7 cm but with a substantial range [6] [1]. One source notes an erect length of 10 cm is near the 5th percentile in a large analysis, underscoring that extremes are uncommon [3].
5. What preferences and perceptions say about size vs. reality
Survey and experimental work show people’s preferences and concerns do not map directly onto population averages. A 2015 experiment using 3D-printed models found women chose an average preferred long-term-partner size of about 16 cm length and 12.2 cm girth—both larger than the clinician-measured population means [2] [7]. Other surveys show many women rate penis size as unimportant; one study reported 77% saying length was unimportant or totally unimportant [2].
6. Measurement method matters: how clinicians measure
Best-practice clinician measurement pushes the pubic fat pad to bone and measures length from pubic bone to tip of glans, and measures circumference at base or mid-shaft; these standardized methods produce more comparable numbers across studies [1] [3]. Sources explicitly caution that different measurement techniques (self-measurement vs. clinician; inclusion of foreskin; non-compression of fat) inflate variability [1] [5].
7. Limitations, disagreements and what’s missing
The cited research gives reliable population averages but does not provide a robust predictive model linking an individual’s erect length to their girth; available sources do not mention a specific scaling law or tight correlation coefficient for length vs. girth in clinician-measured datasets [1] [6]. Sources also note measurement heterogeneity across studies and that self-report inflates estimates [5]. Where surveys report preferred sizes or country rankings, motives (marketing, cultural attention) and selection bias can push numbers upward [7] [8].
8. Practical takeaway for readers
If you want a defensible, clinician-measured benchmark, use erect girth ≈11.66 cm (4.59 in) and erect length ≈13.12 cm (5.17 in) as population averages; expect meaningful individual variation and limited predictability of one measure from the other [1] [3]. For topics of self-image or medical concern, clinical measurement by a professional is the most reliable route and avoids the distortions of self-report [1] [4].