Flaccid spread

Flaccid length is the noisiest figure the measured literature reports, and the data show it directly: its standard deviation, relative to its mean, is wider than stretched or erect length's. That is not a claim about why flaccid length wanders. It is what the pooled numbers themselves look like once you set means and standard deviations side by side.

What "relative to its mean" is doing

Comparing raw standard deviations across states is not quite fair, because flaccid length is itself a smaller number than erect length, so a smaller absolute spread could still represent more relative variation. The comparison that matters is the standard deviation as a fraction of the mean, and on that measure flaccid length comes out wider than stretched or erect. Men vary more, relative to their own average size, in the flaccid state than in either of the other two states the literature reports.

What this data point does and does not tell you

This is a statement about the shape of the pooled distribution, not an explanation of it. The reasons flaccid length varies as much as it does are covered where the mechanism belongs, in the method-side post on why flaccid length wanders. This post is the data-side confirmation: whatever is driving the variation, it shows up as a wider relative spread in the pooled figures, and that agreement between the data and the mechanism is itself worth noting - a self-reported figure could in principle show a wide spread for reasons that have nothing to do with anatomy, so it matters that the clinician-measured pool shows the same pattern.

Why it matters for a percentile

A wider relative standard deviation means a flaccid percentile chart is a blunter instrument than an erect one. The same absolute difference in centimetres moves a man further across a tighter distribution than a wider one, so flaccid percentiles carry more built-in noise before your own measurement error is even added on top. Stretched flaccid length, by contrast, correlates better with erect and is reported with a tighter spread, part of why clinics favour it as a proxy.

If a figure you have seen claims precision down to a fraction of a centimetre for flaccid length specifically, treat that precision as unearned - a wide relative spread at the population level is a reasonable prior for a wide spread in your own repeated readings too. None of this has a bearing on a photograph-based score - Rate Cock, a numeric rating tool, a human judge or an AI estimate from an image are not drawing on a flaccid measurement distribution at all, since none of them are taking a measurement in the first place.