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What are the average erect penis length and girth by age and population?
Executive summary
Most reputable reviews and clinical studies place the average erect adult penis length in the ~5.1–5.5 inch (≈13–14 cm) range and average erect girth around 11.7–11.8 cm (≈4.6–4.7 in) [1] [2]. Growth occurs mainly during puberty and typically plateaus by late teens or early 20s; reported age curves and pediatric charts show large individual variation and different measurement methods produce different averages [3] [4].
1. What the best clinical reviews say about adult averages
Systematic reviews and large clinical datasets measured by health professionals generally converge on an average erect length of about 13.1 cm (≈5.17 in) and an erect circumference of about 11.66 cm (≈4.59 in); the 2015 BJU International review and other syntheses are the clearest single clinical references for those numbers [1] [2]. Media and health outlets commonly summarize that range as roughly 5.1–5.5 inches for length and about 4.6–4.7 inches for girth [5] [6].
2. Why published averages differ: method, self‑reporting and measurement
Studies that rely on self-reported measurements tend to report larger averages than studies with clinician-measured data; review authors and secondary analysts note that self-reporting inflates length by a measurable amount and researchers sometimes adjust self‑reported datasets downward [7] [8]. Wikipedia and clinical reviews explicitly note the measurement method (flaccid, stretched flaccid, erect; pubic bone compression or not) as a primary driver of differences between studies [1].
3. Growth by age — the broad trajectory and typical plateau
Penile growth begins in puberty—typically near ages 10–14 with a common average onset around 12—and most growth in length and girth happens through the teen years; many sources state growth usually stabilizes between the late teens and early 20s (often cited as 16–21) [4] [9]. Pediatric charts and regional growth-curve studies provide age-specific percentile curves (for example, Chinese and other cohorts) showing systematic increases during puberty, but those charts differ by population and sample [3] [10].
4. Age-specific numbers: ranges, not precise “averages”
Public-facing guides and health sites give age-band ranges rather than a single number because individual trajectories vary. Examples include estimates that by mid-to-late adolescence erect length commonly sits in the ~5–6 in (≈12–15 cm) window and that many sources list adult average erect length roughly 5.1–5.7 inches [11] [12] [6]. Available sources do not provide a single, validated table of average erect length and girth by each year of age across multiple populations; instead they offer study- or country-specific percentiles and summary ranges [3] [1].
5. Population and country differences — contested and method‑sensitive
Multiple aggregators and country‑ranking sites publish national averages and maps, but these compilations mix clinical studies with self-reported surveys and apply different corrections; as a result rankings and precise country means vary widely between outlets [13] [8] [14]. WorldPopulationReview, VisualCapitalist and others present country-level maps and lists, but such datasets frequently note methodological caveats and the possibility of sampling bias [13] [14]. Some commercial or advocacy sites present larger global averages (e.g., ~13.9 cm) but those figures reflect aggregation choices and should be interpreted cautiously [15].
6. What matters for interpretation — variation, preferences, and clinical thresholds
Researchers emphasize huge natural variation: studies show most men cluster within a narrow central range but outliers exist, and clinical definitions (for example, micropenis) are based on deviations from population norms (2.5 standard deviations below the mean) rather than an absolute number [5] [16]. Social and sexual‑preference studies also find that partner preferences are often different from male anxieties, and many women in sample studies reported size as less important than commonly believed [2].
7. Practical takeaways and limitations of the reporting
If you want a single evidence‑based anchor: clinical reviews measured by health professionals support an average erect length of ≈13.1 cm (≈5.17 in) and an erect circumference ≈11.66 cm (≈4.59 in) [1]. Expectable variation by age is documented in pediatric growth charts, but available sources do not provide one unified, validated table of average erect length and girth by single‑year age across all populations; national comparisons are especially sensitive to measurement method and sampling bias [3] [8].
If you want, I can pull specific percentile charts from the pediatric growth‑curve studies referenced above or summarize one country’s measured dataset (clinician‑measured only) so you can see age-by-age percentiles and how they compare to the global review figures [3] [1].