What is the average erect and flaccid penis length and girth in large peer-reviewed studies?

1. What the largest clinician‑measured analyses found

A 2015 systematic review that used clinician measurements (to reduce self‑report bias) reported mean values of 9.16 cm flaccid length, 13.12 cm erect length, 9.31 cm flaccid girth, and 11.66 cm erect girth; these figures are widely cited as the best‑quality estimates because staff used standard measuring technique (pressing the pubic fat pad to bone for erect length and measuring circumference at base/mid‑shaft) ^{[1] [2]}.

2. Why different studies report slightly different averages

Meta‑analyses and reviews differ because of measurement method (self‑report vs. clinician measurement), sample selection (volunteer bias — men who participate may not represent the general population), geographic sampling and small study counts in certain regions, and heterogeneous protocols across studies; reviews note this heterogeneity and caution interpretation ^{[5] [1]}. Reviews that include self‑reports tend to give larger means than clinician‑measured datasets ^[1].

3. The consensus range across large reviews

When multiple peer‑reviewed studies are pooled, most reputable summaries give an erect length range near 12.9–13.9 cm (5.1–5.5 in) and erect girth around 11.5–12.2 cm (4.5–4.8 in); one review combining 10 studies of erect measurements reported a combined mean of about 13.6 cm but concluded volunteer bias likely pulls that figure upward toward the top of the range ^{[3] [4]}.

4. Flaccid and “stretched” measures — what they mean and why they matter

Flaccid length averages are smaller (around 9.1 cm in clinician‑measured reviews), and “stretched” length—measured by extending the flaccid penis—gives a value close to erect length in many men (stretched mean reported ≈13.24 cm in systematic review) ^[1]. Clinicians report that flaccid size is a poor predictor for individual erect length because some men are “growers” and some “showers” ^{[1] [6]}.

5. Percentiles, clinical significance, and perception

Large analyses offer percentile tables: for example, an erect length of ~10 cm falls near the 5th percentile in some pooled data, illustrating how clinicians classify “small” vs. “average” ^[2]. Media and lay discussions often amplify concerns about size, but reviews emphasize most men fall within a narrow distribution around the cited means and many partners report satisfaction irrespective of small differences ^{[4] [3]}.

6. Limitations, biases, and what current sources don’t say

Available sources note considerable heterogeneity and explicitly warn about small study counts in regions, inconsistent measurement protocols, and volunteer/self‑reporting bias; they do not provide a single global number free of these limitations ^{[5] [1]}. Current reporting in these sources does not resolve whether subtle population‑level differences by ethnicity or country are clinically meaningful beyond the narrow overall range ^{[5] [4]}.

7. Practical takeaway for readers

For clinicians and lay readers seeking a guideline: expect average erect length near 13.1 cm (≈5.1 in) and erect girth near 11.7 cm (≈4.6 in) if using clinician measurements; broader pooled datasets give a plausible erect length window of 12.9–13.9 cm (5.1–5.5 in) and girth roughly 11.5–12.2 cm (4.5–4.8 in) ^{[1] [3]}. Remember that measurement method, sample selection, and individual variability make exact precision impossible and that reviews urge caution against over‑interpreting small differences ^{[5] [1]}.

If you want, I can extract specific percentile tables, list the largest individual studies included in the major reviews, or show how measurement protocol differences change reported means (noted in the systematic reviews) ^{[5] [1]}.