The register

Method and sources

This page holds every formula we use, every assumption we make, and the complete country table. It exists so you can check our work, and so you can see exactly how shaky the famous numbers are.

A B C D

How are the numbers computed?

Length within a population is treated as approximately normal. The distribution comes from the largest clinical review available, Veale et al. 2015 [1]: clinically measured erect length averages 13.12 cm with a standard deviation of 1.66 cm, which we round to 1.7. Your position is z = (you − country mean) / SD, converted to a percentile with the normal CDF using the Abramowitz–Stegun approximation. We then multiply by the adult male population and report men, not percentiles, rounded to the nearest 10,000 because the inputs do not support more precision.

Note the gap: the clinical mean is 13.12 cm, while the placeholder world mean in our table sits at 13.6 cm, because compiled country figures lean on self-reports. Independent work comparing measured with self-reported studies puts the measured combined mean at 13.61 cm and shows self-reports running well above it [2][3]. That gap is the whole story of this dataset.

What does a stretched measurement tell you?

Almost nothing in the literature measures what you just typed in. A review of the methods used by 70 studies found that 60 % measured the penis stretched while flaccid, and only 27 % ever measured it erect [17]. The register inherits that problem. Of the countries below whose best study yielded a usable figure at all, twelve were measured stretched and seven erect, and two of those seven were the men measuring themselves.

So the whole table depends on whether a stretched measurement can be converted into an erect one. Four credible sources answer that question four different ways.

Source What it is Stretched against erect
Veale 2015 [1] 15,521 men, pooled across studies stretched reads 0.12 cm higher
Wessells 1996 [5] 80 men, both states measured in the same man stretched reads 0.5 cm lower
Belladelli 2023 [15] 55,761 men, pooled across studies stretched reads 1.0 cm lower
Habous 2015 [16] 201 men, both states, seven examiners stretched reads 21.4 % lower, a 2.64 cm gap

The distance between the top row and the bottom row is about 2.8 cm. The entire claimed range in the register below, from the lowest country to the highest, is 7.9 cm. The uncertainty in the single conversion everything depends on is therefore more than a third of the whole effect the famous maps claim to show.

The reasons for the disagreement are mechanical rather than statistical. In the study with seven examiners, different clinicians measuring the same men underestimated erect length by anywhere from 16 to 27 % [16]. And pulling a flaccid penis out to its true erect length takes at least 450 g of tension, while measured examiner force averaged 428 g [15]. The measurement usually stops just short, by an amount that depends on who is holding the ruler.

So we do not convert. Where a country's best study measured stretched, this register says stretched and leaves it there. Publishing a tidy erect figure would mean quietly picking one of those four rows and hoping nobody asks about the other three.

What do we assume?

  • The same SD everywhere. Nobody has set out to measure national standard deviations, so we apply the global one to every country. We did at least check whether that is reasonable: see the next section.
  • Normality. A good approximation near the middle, weaker at the extremes. Percentiles beyond roughly the 99th should be read as illustrations.
  • Length only. Rankings ignore girth entirely, since no country-level girth data exists that is worth publishing.

Is one standard deviation for the whole world defensible?

Reasonably, as long as a clinician did the measuring. These are the spreads actually reported by the national studies we could locate:

Country Study Measure SD (cm)
Egypt Shalaby 2015, n=2,000 stretched 1.35
Turkey Aslan 2011, n=1,132 stretched 1.60
China Meta-analysis 2025, n=34,060 erect 1.63
World Veale 2015, n=15,521 [1] erect 1.66
Iraq Hussein 2017, n=223 stretched 1.90
Egypt Kamel 2009, n=949 stretched 1.90
Italy Di Mauro 2021, n=4,685, self-measured erect 2.55

Clinician-measured spreads sit between 1.35 cm and 1.9 cm, and the 1.7 we use sits in the middle of them. The outlier is the one dataset in the list where the men measured themselves, and its spread is roughly half again as wide as any clinical one. Self-measurement does not only push the average up. It makes the whole distribution baggier, which is a further reason to distrust any national figure derived from it.

How are sources graded?

Every country figure gets a grade from A to D:

  • A: measured by clinicians, published, and we can read the study.
  • B: clinically measured but small, old, or methodologically odd.
  • C: self-reported survey with a described method.
  • D: self-reported with no method, or a study nobody can actually locate. A surprising share of the internet's favourite numbers are D.

How the audit works: every country was checked against the included-study lists of the three systematic reviews of the world measurement literature (Veale 2015 [1], the Belladelli 2023 meta-analysis of 75 studies [15], and the Kaya 2025 review of 33 studies sorted by WHO region [14]), plus targeted searches for the countries with studies. The whole list was then swept a second time, independently, against the Europe PMC database by country. A country appearing in no review, with nothing found on top of that, is marked "none located". If you know a study we missed, the about page tells you where to send it, and we will grade it.

One category sits between "matched" and "none located". Spain, Norway and Poland each appear in the measurement literature exactly once, inside a single drug trial that pooled 423 prostate-cancer patients across eight countries and published no per-country figure. Their men have been measured; their countries have no number. Calling that "no study" would be unfair, and calling it a source would be false, so the register says what it is. The trial measured stretched length only, so even a per-country breakdown would not have answered the question the map claims to answer.

Where do the claimed figures come from?

We traced our own placeholder set, and it matches the widely republished worlddata.info compilation digit for digit: Ecuador 17.61, Cameroon 16.67, Bolivia 16.51, Italy 15.35, and a world mean of 13.59, which is the 13.6 used across this site. That compilation feeds most viral penis-size maps, statistics accounts and listicles, and it publishes no verifiable per-country references. Where we have checked it against locatable studies, the median claim sits half a centimetre above the paper, and the average hides the pattern. Four of the nineteen claims are simply the study's own figure, rounded: Britain, India, Germany and the United States. Where the claim carries a D, meaning nothing solid stands behind it, the median runs a full centimetre high. And for the other hundred countries there is nothing to check it against at all.

We show these numbers deliberately: they are what the internet believes, and the register's job is to grade every claim against a real study until each one is confirmed, corrected, or exposed. When the grading is complete, the calculator and the rankings switch to study-based figures, and countries without a usable study go grey.

If a country has no study, what is the honest fallback?

Three systematic reviews have pooled the world literature. They agree on the shape and disagree on the detail.

Review Studies Men Flaccid Stretched Erect
Veale 2015 [1] 17 15,521 9.16 13.24 13.12
Belladelli 2023 [15] 75 55,761 8.70 12.93 13.93
Kaya 2025 [14] 33 36,883 9.22 12.84 13.84

Only one of the three breaks the world down far enough to be useful as a substitute for a missing country. These are Belladelli's pooled regional means, in centimetres:

Region Flaccid Stretched Erect 95 % CI on erect
Africa 8.09 12.53 14.88 12.50–17.26
Asia 7.23 11.60 11.74 10.18–13.29
Europe 9.44 13.40 14.12 12.53–15.72
North America 9.82 13.75 14.58 13.68–15.48
South America 11.00 15.60 14.50 11.40–17.60
Oceania not reported not reported 15.71 12.73–18.69

Look at the last column before drawing any conclusion. The African erect mean is a single study's worth of evidence stretched across a continent, and its interval runs from 12.5 cm to 17.26 cm. Oceania's is one Australian study of 184 men who measured themselves. Heterogeneity across the pooled studies was 98.9 % [15], which is about as high as that number goes. Note also that South America's stretched mean exceeds its erect mean, which cannot be true of the same men and simply reflects two different sets of studies.

This is the honest fallback, and we do not paste it into the country table. A regional average wearing a national label is precisely the move that produced the numbers we are auditing. It belongs here, with its error bars showing, and nowhere else.

A note on the newest of the three reviews. Kaya 2025 is the only one to sort the world by WHO region, so it is the one we would most like to lean on. Its abstract reports the largest regional flaccid mean as 10.98 cm; its own results section says 9.86 cm. Its abstract gives the largest flaccid circumference as 10.00 cm against 9.74 cm in the results. It lists its regions "in decreasing order" with 10.88 placed ahead of 11.57. And it includes a self-measured study after stating that self-reports were excluded [14]. We cite it because it is the best regional breakdown that exists, and we say all of that because someone should.

What is wrong with this data?

  • Self-reporting. Men round up. Self-reported means run 1–2 cm above clinically measured ones, and many country figures are self-reported.
  • Bone-pressed or not. Pressing the ruler through the fat pad to the pubic bone adds 1.8–2.0 cm. Two studies measured the same men both ways and found 1.81 cm in 778 Saudi men [18] and 2.0 cm in an Egyptian control group [19]. Studies differ in which of the two they report, and that difference alone is larger than most of the gaps between countries in the table below. See how to measure penis size.
  • Tiny samples. Some national figures rest on fewer than 100 men.
  • Different people measuring. Seven andrology specialists measuring 201 of the same men underestimated erect length by between 16 and 27 % depending on which of them held the ruler [16]. Two studies of the same country can disagree for no reason other than that.
  • Ghost studies. Several widely cited national means trace back to studies that cannot be found at all. The famous world maps largely descend from a 2013 compilation whose figures came from unpublished website collections mixing self-report with measurement [13]. Until re-sourced, everything descending from that lineage is grade D by default.
  • And it is not only our problem. In 2016 a Congolese team surveyed 21 sources of public information about penis size in Kinshasa and Lubumbashi. 85.7 % announced a figure without stating any measurement method, and 57.1 % cited no reference at all [20]. DR Congo carries one of the highest claimed figures on every viral map and has no measurement study whatsoever. The correction was published inside the country a decade ago, and nobody redrew the map.

The full register

All 119 claims, reviewed. The verdict: 7 match a locatable study, 21 are contradicted by the best study in their country, 3 appear only inside a pooled multinational sample with no national figure, and 88 have no locatable study at all. That last number is the map nobody publishes.

# Country Claimed mean (cm) Grade Best locatable study Year n Study mean (cm)
1 Ecuador 17.6 D none located
2 Ghana 17.3 D none located
3 Cameroon 16.7 D none located
4 Colombia 16.6 D none located
5 Bolivia 16.5 D none located
6 Sudan 16.5 D none located
7 Haiti 16.0 D none located
8 Netherlands 15.9 D none located
9 Senegal 15.9 D none located
10 Cuba 15.9 D none located
11 Czech Republic 15.9 D none located
12 Belgium 15.8 D Moreira de Goes et al. 1992 17 no usable figure
13 Zambia 15.8 D none located
14 France 15.7 D Bondil et al. 1992 905 no usable figure
15 Brazil 15.7 D Alves Barboza et al., Int J Impot Res 2018 900 no usable figure
16 Angola 15.7 D none located
17 Egypt 15.7 D Shalaby et al., Andrologia 2015 2,000 13.84 stretched
18 Venezuela 15.6 D none located
19 Guatemala 15.6 D none located
20 Georgia 15.6 D none located
21 DR Congo 15.5 D none located
22 Italy 15.4 D Ponchietti et al., Eur Urol 2001 3,300 12.50 stretched
23 Peru 15.4 D none located
24 South Africa 15.3 D none located
25 Iceland 15.3 D none located
26 Zimbabwe 15.2 D none located
27 Paraguay 15.2 D none located
28 Slovakia 15.2 D none located
29 Mexico 15.1 D Ansell condom survey 2001 300 no usable figure
30 Mozambique 15.1 D none located
31 Ivory Coast 15.1 D none located
32 Serbia 15.1 D none located
33 Nigeria 15.0 D Orakwe et al., West Afr J Med 2007 115 13.37 stretched
34 Panama 15.0 D none located
35 Dominican Republic 15.0 D none located
36 Ireland 15.0 D none located
37 Hungary 15.0 D none located
38 Bulgaria 15.0 D Tomova et al. 2010 310 no usable figure
39 Croatia 15.0 D none located
40 Tanzania 15.0 D Chrouser et al., J Urol 2013 253 no usable figure
41 Uganda 15.0 D none located
42 Mali 15.0 D none located
43 Argentina 14.9 B Solé et al., Asian J Androl 2022 800 15.20 stretched
44 Honduras 14.9 D none located
45 El Salvador 14.9 D none located
46 Nicaragua 14.9 D none located
47 Canada 14.9 D Siminoski and Bain 1993 63 no usable figure
48 Denmark 14.9 D none located
49 Bosnia and Herzegovina 14.9 D none located
50 Kenya 14.9 D none located
51 Albania 14.8 D none located
52 Madagascar 14.8 D none located
53 Uruguay 14.7 D none located
54 Austria 14.7 D none located
55 Greece 14.7 D Spyropoulos et al. 2005 52 no usable figure
56 Latvia 14.7 D none located
57 Chile 14.6 D none located
58 Costa Rica 14.6 D none located
59 Ukraine 14.6 D none located
60 Lithuania 14.6 D none located
61 Algeria 14.6 D none located
62 Libya 14.6 D none located
63 Ethiopia 14.6 D none located
64 Somalia 14.6 D none located
65 Germany 14.5 B Schneider et al., Urology 2001 143 14.48 erect
66 Romania 14.5 D none located
67 Slovenia 14.5 D none located
68 Estonia 14.5 D none located
69 Portugal 14.5 D none located
70 Tunisia 14.5 D none located
71 Sweden 14.4 D none located
72 Switzerland 14.4 D none located
73 Israel 14.4 D Chen et al., Int J Impot Res 2000 55 13.60 erect
74 United Kingdom 14.3 B Khan et al., BJU Int 2012 609 14.30 stretched
75 Norway 14.3 D Brock et al. (pooled multinational trial) 2015 423 no usable figure
76 Poland 14.3 D Brock et al. (pooled multinational trial) 2015 423 no usable figure
77 Belarus 14.3 D none located
78 United States 14.2 C Herbenick et al., J Sex Med 2014 1,661 14.15 erect
79 Morocco 14.2 D none located
80 Jordan 14.2 D Awwad et al., Int J Impot Res 2005 271 13.50 stretched
81 Turkey 14.1 B Söylemez et al., Int J Impot Res 2012 2,276 13.98 stretched
82 Finland 14.0 D none located
83 Armenia 14.0 D none located
84 Spain 13.9 D Brock et al. (pooled multinational trial) 2015 423 no usable figure
85 New Zealand 13.9 D none located
86 Syria 13.9 D none located
87 Iraq 13.6 D Hussein et al., Arab J Urol 2017 223 12.60 stretched
88 Yemen 13.6 D none located
89 Japan 13.5 D Kadono et al. 2017 102 12.60 stretched
90 Azerbaijan 13.5 D none located
91 Kazakhstan 13.5 D none located
92 Saudi Arabia 13.5 D Habous et al., J Sex Med 2015 778 14.34 erect
93 Pakistan 13.5 D none located
94 United Arab Emirates 13.5 D none located
95 Iran 13.4 D Mehraban et al., Int J Impot Res 2007 1,500 11.58 stretched
96 Australia 13.3 D Smith et al., Int J STD AIDS 1998 184 15.71 erect
97 Uzbekistan 13.3 D none located
98 Kyrgyzstan 13.3 D none located
99 Russia 13.2 D none located
100 Afghanistan 13.2 D none located
101 Turkmenistan 13.2 D none located
102 India 13.0 B Promodu et al., Int J Impot Res 2007 301 13.01 erect
103 Nepal 12.9 D none located
104 China 12.9 B Wang and WangDing, Andrology (meta-analysis) 2025 34,060 12.42 erect
105 Bangladesh 12.8 D none located
106 Mongolia 12.8 D none located
107 Sri Lanka 12.7 D none located
108 Papua New Guinea 12.0 D none located
109 Indonesia 11.7 D none located
110 Malaysia 11.6 D none located
111 Vietnam 11.5 D Nguyen Hoai et al., Andrology 2021 14,597 14.67 stretched
112 Thailand 11.5 D none located
113 Laos 11.0 D none located
114 Philippines 10.9 D none located
115 Myanmar 10.9 D none located
116 South Korea 10.8 D Son et al., Asian J Androl 2003 123 9.60 stretched
117 Taiwan 10.8 D Chen et al. 1992 40 no usable figure
118 Cambodia 10.0 D none located
119 North Korea 9.7 D none located

The corrections

What the audit turned up in every country we chased individually, including the ones where the chase came back empty. Study links where a stable one is available. The 87 countries not listed here were swept with the reviews and the database search and produced nothing to chase, Ecuador and its famous 17.6 included.

  • Argentina B : The claimed 14.9 sits just under the 15.2 cm stretched mean Solé 2022 measured in 800 men across four hospitals, the largest study in South America. As so often, a stretched figure wearing an erect label. The same study found little or no correlation between penis size and height, weight or foot length. Study
  • Australia D : The only Australian study is self-measured: 15.71 cm in 184 condom-study volunteers, which mainly demonstrates the self-report problem. The claimed 13.3 matches nothing at all. Study
  • Belgium D : Seventeen men in 1992 is the entire Belgian evidence base. The claimed 15.8 is unsupported.
  • Brazil D : Brazil has real studies: 900 volunteers measured stretched in 2018 (a study explicitly framed as testing a myth), 689 elderly urology patients, and a small 1994 erect series of 150 men. None of them supports the claimed 15.7. Study
  • Bulgaria D : Tomova 2010 measured flaccid length only. Nothing supports the claimed 15.0 erect.
  • Canada D : The only Canadian data is a 1993 height-and-foot-size correlation paper that measured stretched length in 63 volunteers. The claimed 14.9 rests on nothing.
  • China B : China is the best-evidenced country in the register. A 2025 meta-analysis pooled 23 studies and 34,060 men to 12.42 cm erect (SD 1.63), and the largest single study, Chen 2014, found 12.9 cm stretched in 5,196 men and 12.9 cm erect in a 311-man subgroup. The claimed 12.9 lands about half a centimetre high, and no other country in this table has this much evidence behind the comparison. Study
  • Egypt D : Three Egyptian studies now exist, all clinician-measured, none supporting the claim. Kamel 2009 measured 949 men at 12.9 cm stretched, Shalaby 2015 measured 2,000 at 13.84 cm stretched, and Salama's 2016 controls were measured erect at 13.0 cm, or 15.0 cm with the ruler pressed to the bone. The compilation's 15.7 is close to only that last figure, from the smallest sample of the three. Study
  • France D : No French study has ever measured erect length. Bondil 1992 measured flaccid and stretched in 905 urology patients. Where the compilation's 15.7 comes from is anyone's guess.
  • Germany B : Matches Schneider 2001, one of very few studies to measure erect length properly (14.48 cm in young men). Small sample of 143, hence B. Study
  • Greece D : The only Greek study measured 52 urology patients, stretched. The claimed 14.7 cannot be traced to it.
  • India B : Matches Promodu 2007 almost exactly: 13.01 cm measured erect. The erect subgroup was only 93 men, hence B. Study
  • Iran D : Mehraban 2007 measured a random sample of 1,500 men: 11.58 cm stretched. The claimed 13.4 floats 1.8 above it. Study
  • Iraq D : Hussein 2017 measured 223 healthy men in Baghdad and published a proper nomogram, with a stretched mean of 12.6 cm and a median of 12.5. The claimed 13.6 floats a centimetre above it. Study
  • Israel D : Chen 2000 measured 55 patients with induced erections: 13.6 cm. The claimed 14.4 overshoots the only real measurement. Study
  • Italy D : The internet says 15.4. The largest clinician study measured 3,300 young men at 12.5 cm stretched and never measured erect at all. The largest Italian dataset of any kind, Di Mauro 2021, asked 4,685 men to measure themselves at home and got 16.78 cm erect. The claim sits between a clinical measurement and a self-measurement, matching neither, which is how these figures are made. Study
  • Japan D : Kadono 2017 measured about a hundred clinic patients: roughly 12.6 cm stretched. The claimed 13.5 erect matches no Japanese measurement.
  • Jordan D : Awwad 2005 measured 271 healthy men: 13.5 cm stretched. Erect length was only measured in patients with erectile dysfunction, so the compilation's 14.2 erect has no source. Study
  • Mexico D : The only entry in the literature index is a condom manufacturer's promotional survey from 2001. That is the entire evidence base behind the claimed 15.1.
  • Nigeria D : Orakwe 2007 found 13.37 cm stretched in 115 men and never measured erect. A second study, Takure 2021, measured 271 men and reported 10.6 cm stretched under 50 and 14.1 cm over 50, an age pattern running the wrong way and hard to credit. The compilation's 15.0 sits above every Nigerian measurement on record.
  • Norway D : Norwegian men have been measured, but only inside the same 423-man, eight-country trial baseline, with no national figure published. The claimed 14.3 has nothing to be checked against. Study
  • Poland D : Poland's only appearance in the literature is inside that same pooled trial baseline. Saying no Polish study exists would be slightly unfair; saying a Polish figure exists would be simply false. Study
  • Saudi Arabia D : Habous 2015 induced erections pharmacologically in 778 men and measured 14.34 cm bone-pressed, 12.53 without pressing. The compilation's 13.5 matches neither. Study
  • South Korea D : Son 2003 measured 123 conscripts: 9.6 cm stretched. The compilation's 10.8 erect is not from any locatable study. Belladelli's index also lists a 309-man Korean series measured erect (Park 2011) that we have not yet been able to read; it would be the better source once obtained.
  • Spain D : Spain appears in the world measurement literature exactly once: as part of the baseline of a drug trial in prostate-cancer patients that pooled 423 men across eight countries and published no per-country figure. There is no Spanish estimate for the claimed 13.9 to agree or disagree with. Study
  • Sweden D : No Swedish measurement study could be located at all. The 14.4 is pure compilation.
  • Taiwan D : A single 40-man study from 1992 is all that exists. The claimed 10.8 rests on it at best.
  • Tanzania D : Chrouser 2013 measured adults at about 11.5 cm unstretched to size circumcision devices, with no stretched or erect data. The claimed 15.0 is unsupported.
  • Turkey B : The 14.1 sits right at Söylemez 2012's stretched mean from 2,276 men (a second study of 1,132 men found 13.7), relabelled as erect somewhere along the way. The closest thing to an honest number in the compilation. Study
  • United Kingdom B : Khan 2012 measured 609 British men: 14.3 cm stretched, exactly the claimed figure, relabelled as erect somewhere along the way. Same pattern as Turkey. Study
  • United States C : The compilation figure matches Herbenick 2014, a real study of 1,661 men who self-measured erect to receive a fitted condom. A decent incentive to be honest, but still self-reported, hence C. Study
  • Vietnam D : The rare case where the internet understates. 14,597 men measured at clinics gave a median of 14.67 cm stretched, against the compilation's 11.5. Study

Want the raw files? The dataset page explains what will be published, and why the placeholder set is not downloadable yet.

References

Every health claim on this site traces to one of the sources below. This is the whole site's bibliography, not just this page's, so the numbered markers above skip the entries that are cited on the condom, measurement and testicular pages instead. The country table above is the part still being sourced, and is labelled accordingly.

  1. 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. PubMed 25487360. Clinically measured erect length 13.12 cm (SD 1.66); erect circumference 11.66 cm (SD 1.10).
  2. King BM. Average-size erect penis: fiction, fact, and the need for counseling. Journal of Sex and Marital Therapy 2021; 47(1): 80–89. PubMed 32666897. Combined mean of measured studies 13.61 cm; self-reported figures run substantially higher.
  3. King BM, Duncan LM, Clinkenbeard KM, Rutland MB, Ryan KM. Social desirability and young men's self-reports of penis size. Journal of Sex and Marital Therapy 2019; 45(5): 452–455. PubMed 30681032.
  4. Lever J, Frederick DA, Peplau LA. Does size matter? Men's and women's views on penis size across the lifespan. Psychology of Men and Masculinity 2006; 7(3): 129–143. Full text. Of 52,031 respondents, 85 % of women were satisfied with their partner's size, while 55 % of men were satisfied with their own.
  5. Wessells H, Lue TF, McAninch JW. Penile length in the flaccid and erect states: guidelines for penile augmentation. Journal of Urology 1996; 156(3): 995–997. The bone-pressed measurement technique, and augmentation guidance reserved for far below the normal range.
  6. ISO 4074. Natural rubber latex male condoms: requirements and test methods. Defines nominal width as half the flat circumference.
  7. Crosby RA, Yarber WL, Graham CA, Sanders SA. Does it fit okay? Problems with condom use as a function of self-reported poor fit. Sexually Transmitted Infections 2010; 86(1): 36–38. PubMed 20157178. Ill-fitting condoms carried 2.6 times the odds of breakage and 2.7 times the odds of slippage.
  8. Penis enlargement products: do they work? Mayo Clinic. mayoclinic.org.
  9. Micropenis. StatPearls, NCBI Bookshelf. NBK562275. Stretched length more than 2.5 SD below the age-adjusted mean; adult threshold about 9.3 cm. See also Hatipoğlu N, Kurtoğlu S, Journal of Clinical Research in Pediatric Endocrinology 2013, PMC3890219.
  10. Key statistics and survival rates for testicular cancer. American Cancer Society. cancer.org. Most common solid tumour in men aged 15–34; five-year survival about 95 % overall and 99 % when localized.
  11. Testis fact sheet, Cancer Today (Globocan 2024 estimates). International Agency for Research on Cancer, WHO. gco.iarc.who.int. An estimated 70,714 new cases and 9,240 deaths worldwide per year; Europe carries 35 % of cases but 18 % of deaths.
  12. US Preventive Services Task Force. Screening for testicular cancer: reaffirmation recommendation statement. Annals of Internal Medicine 2011; 154(7): 483–486. uspreventiveservicestaskforce.org. Grade D against population screening, self-examination included: cited on the check yourself page as the honest caveat, alongside the NHS and ACS guidance on knowing your own baseline.
  13. Lynn R. Rushton's r-K life history theory of race differences in penis length and circumference examined in 113 populations. Personality and Individual Differences 2013; 55(3): 261–266. Cited as provenance, not as evidence: this paper is the main ancestor of the viral country maps, its figures trace to unpublished website compilations, and its author's broader body of work is widely criticized as methodologically flawed. The register treats every figure descending from it as grade D pending re-sourcing.
  14. Kaya E, et al. A systematic review and meta-analysis of penis length and circumference according to WHO regions: who has the biggest one? Urology Research and Practice 2025. PubMed 40248849. 33 studies, 36,883 men, clinician-measured only. Source of the WHO-region breakdown, and of the internal contradictions noted above.
  15. Belladelli F, Del Giudice F, Glover F, et al. Worldwide temporal trends in penile length: a systematic review and meta-analysis. World Journal of Men's Health 2023; 41(4). PubMed 36792094. 75 studies, 55,761 men, 1942–2021. Pooled flaccid 8.70 cm, stretched 12.93 cm, erect 13.93 cm. Erect length rose 24 % across 29 years. I² = 98.9 %. Its Table 1 is the backbone of this register's audit, and the source of the 450 g stretching force figure.
  16. Habous M, Muir G, Soliman T, et al. Analysis of the interobserver variability in penile length assessment. Journal of Sexual Medicine 2015; 12(10). PubMed 26440678. 201 men, seven examiners: stretched measurement underestimated erect length by 2.64 cm (21.4 %), with interobserver variation from 16 to 27 %.
  17. Cakir OO, Pozzi E, Castiglione F, et al. Penile length measurement: methodological challenges and recommendations, a systematic review. Journal of Sexual Medicine 2021; 18: 433–439. PubMed 33648901. Of 70 studies, 60 % measured stretched length and only 27 % measured erect.
  18. Habous M, Tealab A, Williamson B, et al. Erect penile dimensions in a cohort of 778 Middle Eastern men: establishment of a nomogram. Journal of Sexual Medicine 2015; 12(6). PubMed 25904106. Erect length 14.34 cm measured to the pubic bone against 12.53 cm measured from the skin, in the same men.
  19. Salama N. Consultation for small-sized penis in the Egyptian males: a case control study. American Journal of Men's Health 2016. PubMed 25563384. Controls measured 13.0 cm erect from the skin and 15.0 cm to the bone. Of 239 men who presented convinced they were too small, not one measured below 7 cm erect.
  20. Mulenga PC, Kazadi AB. Informations inexactes sur la taille du pénis en République Démocratique du Congo: à propos de 21 sources d'information. Pan African Medical Journal 2016. PubMed 28154646. Of 21 sources broadcasting a penis size in Kinshasa and Lubumbashi, 85.7 % gave no measurement method and 57.1 % gave no reference.