How do average penis size statistics vary by age and region?
Executive summary
Published meta-analyses and 2025 compilations put global average erect penis length roughly between 13.0–13.9 cm (about 5.1–5.5 in), with country lists reporting wider spreads (e.g., Ecuador ~17.6 cm vs Thailand ~9.4 cm) that reflect methodological differences and sampling biases [1] [2] [3]. Age effects are disputed: a systematic review found erect length increased over decades after adjusting for age but did not isolate strong within-lifetime declines, while several 2025 summaries report little consistent age-to-age variation or only small declines in older men [1] [4] [5].
1. What the best-reviewed evidence shows: a surprisingly narrow global mean
A systematic review and meta-analysis pooling many studies reports pooled means of flaccid 8.70 cm, stretched 12.93 cm, and erect 13.93 cm (95% CI 13.20–14.65), and explicitly notes geographic variation but not radical worldwide differences in the pooled erect mean [1]. That 13–14 cm band appears repeatedly in scientific syntheses and is the anchor for later country-level compilations [1].
2. Country rankings amplify differences largely because of methods and sampling
Web compilations that rank countries produce much wider headline differences—examples include a 142-country analysis listing a global average erect length of 13.12 cm with Ecuador at 17.59 cm and Thailand at 9.43 cm [2], and other sites listing ranges “between 4 and 7 inches” (roughly 10–18 cm) [3]. These lists pull together disparate studies with mixed measurement protocols (self-report, clinical measurement, population vs clinic samples) and therefore magnify apparent regional gaps [3] [2].
3. Age patterns: small or inconsistent changes rather than dramatic life‑course decline
Available syntheses disagree about a simple age‑trend. The systematic review reports that erect penile length increased over time across studies after adjustment for region and age, but it does not present a clear within-person decline with age; other 2025 summaries state “average erect penis length and girth do not differ significantly across age groups” though they acknowledge erectile function declines with age [1] [4]. A commercial 2025 survey claims ages 20–39 had the highest averages and men over 60 averaged 0.4 in (≈1 cm) less, but that report is not a peer‑reviewed meta‑analysis and uses photographic/self‑report protocols whose reliability is debated [5].
4. Why reported regional differences are often overstated
Several sources warn that compiling multinational data uses many small studies with different measurement points (base-to-tip vs stretched, flaccid vs erect), self-report bias, non‑representative samples, and inconsistent age/health controls—so country rankings must be read with caution [3] [2]. The systematic review explicitly adjusted for region, subject age and population and still found only modest regional variation relative to the pooled mean [1].
5. Conflicting claims and the role of non‑peer‑reviewed 2025 surveys
Recent 2025 online surveys and blogs present striking rankings and causal narratives (genetics, nutrition, endocrine disruptors), but these often combine self-report, photographic checks, and selective clinical measures; such methods can reduce some bias but are not the same as blinded, standardized clinical sampling and often come from sites with commercial interest in the topic [5] [6]. Those commercial reports claim larger effect sizes by region and age than the peer‑reviewed meta‑analysis supports [5] [1].
6. What is reliably known and what remains uncertain
Reliable: pooled erect means center around 13–14 cm and many papers report only modest geographic differences after adjustment [1]. Uncertain: precise country ranks and how much average size shifts within a man’s lifespan—available sources do not present a consensus showing large age-related shrinkage [4] [5] [1]. Claims about environmental drivers or large genetic clusters are plausible hypotheses in some 2025 reports but are not established in the systematic review [5] [1].
7. Practical takeaway for readers
Treat global averages (≈13–14 cm erect) as the most robust finding [1]. Treat dramatic country-by-country lists and small decade‑scale or age‑group differences with skepticism unless they come from standardized, peer‑reviewed sampling; the methodological caveats listed by WorldData and other compilers explain much of the spread [3] [2]. When sources disagree, prioritize peer‑reviewed syntheses for population averages and view single‑method 2025 surveys as suggestive but not definitive [1] [5].
Limitations: this summary relies on the cited systematic review and a set of 2025 compilations; available sources do not include a single global, uniformly measured longitudinal cohort that would settle age and regional causation conclusively [1] [2].