What is the average erect penis length according to medical studies?
Executive summary
Medical research reviews place the average erect adult penis length in a narrow range around 13–14 cm (about 5.1–5.5 in); several large meta-analyses report pooled erect means of roughly 13.1 cm, 13.8 cm, and 13.9 cm depending on included studies and methods (examples: 13.12 cm, 13.84 cm, 13.93 cm) [1] [2] [3]. Results vary by measurement method, sample selection and geography; authors warn volunteer bias and regional differences can push pooled estimates slightly higher or lower [4] [5].
1. What the major reviews say: convergence around ~13–14 cm
Three systematic reviews/meta-analyses cited in current reporting give pooled erect means clustered near 13–14 cm. A nomogram-focused review reported an erect mean of 13.12 cm (SD 1.66, n = 692 measured erect) [1]. A WHO-region meta‑analysis pooling 5,669 measured erect penises found a mean erect length of 13.84 cm (SE 0.94) [2] [5]. A global temporal meta‑analysis reported pooled erect length of 13.93 cm (95% CI 13.20–14.65) [3]. Those figures translate to roughly 5.1–5.5 inches, the range commonly quoted in clinician-facing summaries [4] [6].
2. Why reported averages differ: methods, selection and geography
Differences between studies stem from how erect length was obtained (spontaneous or pharmacologic erection, measured by clinician versus self‑report), sample selection (clinical vs. general-population, volunteers), and geography. The WHO‑region meta‑analysis and others explicitly restricted to clinician‑measured samples to reduce self‑report bias, but still found regional variation in mean lengths [2] [5]. The temporal meta‑analysis found erect length estimates vary by region and have increased in pooled data over time after statistical adjustment [3].
3. Volunteer bias and measurement practice push averages around
Authors of reviews note volunteer bias — men who participate in size studies may differ from the general population — and measurement differences likely push some pooled means upward; one review concluded the "true" average is probably toward the lower end of the 5.1–5.5 in range after accounting for bias [4] [6]. Some studies measured stretched or flaccid length and used conversions; stretched length pooled means (around 12.8–13.3 cm) are often similar but not identical to erect measurements and can introduce error if compared directly [2] [1].
4. Regional and temporal patterns: not a single global number
Meta-analyses that subgroup by world region report real differences: e.g., European erect means reported around 14.9 cm in some pooled regional analyses, while global pooled ranges reported in other work span roughly 12.1–15.4 cm depending on included populations and methods [7] [2]. A temporal review also reported an increase in pooled erect length over recent decades after adjustment for confounders [3]. Those patterns suggest a single global “average” oversimplifies underlying heterogeneity.
5. How to interpret an individual’s size — clinical context matters
Nomograms and pooled distributions exist to show variation: one systematic review constructed nomograms from thousands of flaccid, stretched and erect measurements to help clinicians counsel patients; their erect mean (from measured samples) was 13.12 cm with SD 1.66, indicating most adult erect measurements fall within a couple of centimetres of that mean [1]. Medical reviewers stress that perceived “smallness” is often subjective and that clinically significant short penis conditions are rare; some men seek counseling or surgery out of dissatisfaction rather than objective abnormality [4] [7].
6. Limitations in the literature and remaining disagreements
Available studies differ in inclusion criteria, measurement technique, sample sizes and whether measurements were clinician‑taken or self‑reported; risk-of-bias assessments in the cited meta‑analyses vary from low to moderate [2] [5]. Some regional meta-analyses (e.g., a 2024 China-focused paper) report higher regional erect means (around 14–15 cm) which conflict with other pooled global estimates, illustrating that geography, exclusion rules and study selection materially change outcomes [7]. Authors explicitly warn against overgeneralizing a single number [4].
7. Bottom line you can cite
When asked for a concise, evidence-based figure: the peer-reviewed systematic reviews and meta‑analyses in current reporting converge on an average erect adult penis length of about 13–14 cm (approximately 5.1–5.5 inches), with credible pooled estimates reported as 13.12 cm [1], 13.84 cm [2], and 13.93 cm [3]. Interpret that range in light of measurement methods, sample selection and regional variation noted in the cited analyses [4] [5].