Mark first

Mark the girth site on the skin with a small skin-safe dot before wrapping the tape, and write down its distance from the base. A girth reading is only comparable to another one taken at the same site, "the same site" is harder to hit twice by eye than it sounds, and a mark fixes that for very little effort.

Why the site drifts without one

Finding the midpoint by eye, each time, from scratch, introduces a small variation every session - a few millimetres one way or another, which sounds trivial until you remember that girth changes measurably over short distances along the shaft for a lot of people. A site that drifts by half a centimetre between sessions can move the reading by an amount that looks like a real difference and is not.

What to do

Find the site once, using whatever method you use to locate it - measuring the distance from the base is the reliable version, rather than eyeballing "the middle." Mark it with a skin-safe pen, a small dot rather than a ring, placed exactly where the tape's zero edge should sit. Survey anthropometry works the same way: the CDC's NHANES Anthropometry Procedures Manual (2021) has examiners make all body marks with a wax-based cosmetic pencil and wrap the tape at the level of the mark. Wrap the tape so it passes over the mark, and read.

The mark also solves a second problem: it separates finding the site from wrapping the tape, which are two different fine-motor tasks that are easy to fumble at once. Doing them one after another, with the mark holding the site steady in between, is more repeatable than doing both simultaneously.

Record it, don't just mark it

The mark helps on the day. What helps across sessions is writing down the site's distance from the base in the measurement log, next to the reading itself. A mark washes off. A number in a log does not, and it is what lets a reading taken next month land on the same site as one taken today, even without a fresh mark to guide it.

What this is not

This is a technique note about circumference, not a broader claim about anatomy or anything worth tracking over time - remeasuring for its own sake is rarely worth the effort regardless of how precisely the site is marked. It also has nothing to do with how a shaft photographs or reads to a viewer, which is a separate, subjective exercise handled by other kinds of services entirely - a rating from Rate Cock, a score from a photo-based tool, a human reviewer's impression on a site built around that, or an AI model's read of an image, which works from pixels rather than a marked site on skin. None of those depend on where a pen mark sits. A girth reading does.