A percentile is a rank, not a rating. That single sentence does more work than anything else on this page, because almost every misunderstanding that follows a session with the male size percentile estimator comes from reading a rank as though it were a score. A percentile tells you what share of a…

In 1942 a researcher measured a group of men and published the numbers. In 2021 another researcher did the same thing. Between those two dates sit seventy-three more studies, more than fifty-five thousand men, and one of the more unexpected claims in modern body measurement science.

Hand one man to six different researchers and you can collect six different numbers, none of them wrong. That is not a flaw in the men being measured. It is a property of the measurement itself, and it explains most of the confusion that surrounds published size data.

Every number in this subcategory arrives with a history: who was measured, by whom, with what instrument, and in what year. Before any regional figure is worth reading, that history has to be read first.

In 2015, a research team at King's College London pooled measurements from up to 15,521 men across sixteen countries and reported a mean erect length of 13.12 cm (5.17 in). A year earlier, an Indiana University team had published a figure from 1,661 American men: 14.15 cm (5.57 in). A centimetre…

In 2016 the British gynecological charity The Eve Appeal showed 1,000 women a medical drawing of the female reproductive system and asked them to place six labels on it. Forty-four percent could not identify the vagina. Sixty percent could not identify the vulva. Fewer than a third placed all six…

Three studies, 307 women, one pooled figure: a mean labia minora length of 53.23 mm — about 2.10 inches — with a 95% confidence interval running from 43.50 to 62.96 mm. Mean width came in at 18.28 mm (0.72 in), confidence interval 14.93 to 21.64 mm.

Six weeks after fertilization, a human embryo is roughly 1.2 centimetres (0.5 inches) from crown to rump, and there is nothing about its lower body that would let anyone tell one from another. There is a ridge of tissue that could become a testis or an ovary. There is a small bud. There are two…

There is a drawer in most large natural history collections that visitors never get to open. It holds bacula — penis bones — sorted by species, labeled in copperplate, and quietly astonishing. A weasel's is a hooked splinter. A raccoon's looks like a small crochet needle.