The averages, from clinician-measured data
Every figure on this page comes from one source: Veale D, Miles S, Bramley S, Muir G, Hodsoll J, "Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15,521 men," BJU International 2015;115(6):978-986. It pooled only studies where a health professional did the measuring. That matters, and we will come back to why. A quick word first, though, because we know why most people are on this page: the internet's numbers come from self-reported surveys and men round up, so nearly everyone who compares themselves to those figures feels below average. The clinical numbers below are smaller than what you have heard, and wherever you land, you are in a distribution of 15,500 ordinary men. There is a longer version of that thought, and a personal percentile, on our penis size percentile calculator.
| Measurement | Mean (cm) | SD (cm) | Mean (in) | SD (in) |
|---|---|---|---|---|
| Erect length | 13.12 | 1.66 | 5.17 | 0.65 |
| Erect girth (circumference) | 11.66 | 1.10 | 4.59 | 0.43 |
| Flaccid length | 9.16 | 1.57 | 3.61 | 0.62 |
| Flaccid girth (circumference) | 9.31 | 0.90 | 3.67 | 0.35 |
Girth means circumference: the full distance around the shaft at its thickest point, the way you would measure with a tape.
Percentile chart
The Veale nomograms model each measurement as approximately normally distributed, so any percentile can be computed from the mean and standard deviation above. The table below was computed with the same normal-distribution code that powers our percentile calculator, and our automated tests verify every cell against it. Values are cm, with inches in parentheses.
| Percentile | Erect length | Erect girth | Flaccid length | Flaccid girth |
|---|---|---|---|---|
| 5th | 10.4 (4.09) | 9.9 (3.88) | 6.6 (2.59) | 7.8 (3.08) |
| 10th | 11.0 (4.33) | 10.3 (4.04) | 7.1 (2.81) | 8.2 (3.21) |
| 25th | 12.0 (4.72) | 10.9 (4.30) | 8.1 (3.19) | 8.7 (3.43) |
| 50th | 13.1 (5.17) | 11.7 (4.59) | 9.2 (3.61) | 9.3 (3.67) |
| 75th | 14.2 (5.61) | 12.4 (4.88) | 10.2 (4.02) | 9.9 (3.90) |
| 90th | 15.2 (6.00) | 13.1 (5.15) | 11.2 (4.40) | 10.5 (4.12) |
| 95th | 15.9 (6.24) | 13.5 (5.30) | 11.7 (4.62) | 10.8 (4.25) |
Read the width of that table, not just your row. Ninety percent of men fall between the 5th and 95th percentile rows, which for erect length is 10.4 to 15.9 cm (4.1 to 6.2 in). Normal is a wide band, not a point.
The formula
μ and σ are the mean and standard deviation from the first table, Φ is the standard normal cumulative distribution function (we evaluate it with the Abramowitz and Stegun 7.1.26 error-function approximation, accurate to about seven decimals), and zp is the standard normal value for percentile p. Inches convert at 1 in = 2.54 cm.
Worked example
Unit conversion: 5 in × 2.54 = 12.7 cm. Going the other way, 12 cm ÷ 2.54 = 4.72 in.
Percentile lookup: an erect girth of 12 cm gives z = (12 − 11.66) / 1.10 = 0.309, and Φ(0.309) = 0.621, so about the 62nd percentile: larger than about 62 of 100 men in the study.
Why clinical numbers run smaller than internet numbers
Two reasons, both boring and both decisive. First, self-report: in anonymous surveys men round up, sometimes a little, sometimes a lot, and nobody checks. Studies where a clinician measures with a stated protocol consistently land 1 to 2 cm below survey averages, and the Veale review used only measured data. Second, protocol: bone-pressed versus non-bone-pressed, fully erect versus stretched flaccid, and tape placement each move the result by real millimeters. When you see an "average" online with no methods attached, it is closer to folklore than data. If comparing yourself to the honest numbers still leaves you uneasy, that reaction is common and worth taking seriously: if size worries weigh on you, that is a real and common concern worth raising with a doctor or therapist, and it responds well to being talked about.
Putting the numbers to practical use: the percentile calculator gives you your personal position in this data, the condom size calculator turns a girth measurement into a nominal-width recommendation, and the size visualizer draws any measurement to scale so centimeters stop being abstract.