What percentile values for erect penis length did Veale et al. (2015) include in their nomograms (i.e., the 25th, 50th, 75th percentiles)?
Executive summary
Veale et al. reported an erect penis mean of 13.12 cm with a pooled standard deviation of 1.66 cm and used simulated normal distributions to build their nomograms [1]. Translating that reported mean and SD into standard normal percentiles yields approximate erect-length values of 12.00 cm (25th percentile), 13.12 cm (50th percentile/median), and 14.24 cm (75th percentile) under the same normal-distribution assumption used by the authors [1] [2].
1. What the paper actually provided and how the nomograms were constructed
Veale and colleagues performed a systematic review and pooled measurements to create nomograms for flaccid, stretched and erect penile dimensions, explicitly reporting an erect-length pooled mean of 13.12 cm and pooled standard deviation 1.66 cm, and noting that they simulated 20,000 observations from a normal distribution to generate the nomograms [1]; the erect-length sample contributing to that pooled estimate was relatively small (n = 692) compared with other measures, a limitation the authors acknowledged [1].
2. How percentiles are derived from the paper’s reported numbers
Because the paper reports a pooled mean and SD and because the authors modeled distributions via normal simulation, percentile estimates follow directly from the standard normal z-scores applied to mean ± z*SD; using z = −0.674 for the 25th percentile and z = +0.674 for the 75th yields 13.12 − (0.674×1.66) ≈ 12.00 cm for the 25th, the median (50th) equals the mean 13.12 cm, and 13.12 + (0.674×1.66) ≈ 14.24 cm for the 75th [1] [2].
3. Cross-checks and consistency with other summaries and popular reporting
Popular summaries of the study (for example, media coverage cited by WBUR) used the same central values and described approximate percentile landmarks — e.g., reporting that an erect length of 11 cm is near the 10th percentile and 15 cm near the 85th — which is consistent with the 13.12±1.66 distribution implied by Veale et al. [3] [1]; independent calculators and reference pages likewise use Veale’s 13.12±1.66 values to compute percentiles [2].
4. Important caveats and limits of precision
These percentile point estimates assume the pooled erect-length distribution is well approximated by a normal distribution — an assumption Veale et al. explicitly used for their nomograms — and they inherit the limits the authors described: relatively few clinically measured erect values and heterogeneity across source studies, so percentile values are approximate and sensitive to sampling and measurement differences [1]; if the underlying distribution were skewed or multimodal, exact percentile cutoffs could shift, and the primary sources do not publish a ready table of the 25th/50th/75th numeric cutoffs in the text available in the provided reporting [1] [4].
5. Bottom line — the numeric answers, clearly stated
Using Veale et al.’s reported erect mean (13.12 cm) and SD (1.66 cm) and the normal-distribution approach they used to construct nomograms, the approximate erect-length percentiles are: 25th ≈ 12.00 cm, 50th (median) = 13.12 cm, and 75th ≈ 14.24 cm [1] [2]. These are the best numeric translations available from the paper’s reported parameters and the authors’ simulation approach; the original nomogram figures in the paper serve the same purpose graphically [4].