Measuring a mole in millimeters: growth over time and a diary

Without an object of known size a photograph carries no scale: the same mole occupies a different number of pixels at ten centimeters and at forty. A coin solves that precisely — its diameter is standardized to hundredths of a millimeter. The edge of a bank card (85.6 mm) and an ordinary ruler work too. What matters is that the reference lies next to the mole and in the same plane: a centimeter of depth offset at twenty centimeters introduces about five percent of error, which is exactly the quantity we are chasing over six months.

It is the D of the classic ABCDE scheme — a landmark, not a verdict. Plenty of entirely ordinary moles are larger than six millimeters, and some melanomas are smaller. Size on its own is a weak sign; the strong one is a change in size. That is why the tool reacts far more firmly to "grew by two millimeters" than to "six and a half".

With a calm picture, every three months — the usual self-examination interval. With one sign from the scheme, every two months; with two or more, monthly. The tool sets the interval itself and can export reminders to a calendar. Between scheduled shots, any noticed change is reason enough for an extra one.

The observation that one person's moles resemble each other, as if from one family. The one worth attention is the one that does not fit — in size, color or shape. The tool computes this against the median of your own moles rather than the mean, so one large mole does not skew the comparison. The rule starts working from about four pinned moles.

Because that requires a dermatoscope, a trained eye and, in doubt, histology. Apps that give a risk assessment from a photograph are registered as medical devices in Europe — a separate procedure with trials and liability. We have not been through it and will not pretend otherwise. Measuring, on the other hand, is allowed — and it is precisely the part a person cannot do alone.

Immediately if a mole bleeds without injury, crusts over, ulcerates or becomes a nodule. Without delay if three signs coincide (asymmetry, ragged border, uneven color), if it has visibly grown, if it stands out sharply from your others, or if a new lesion appeared after thirty and looks unlike the rest. The tool names these reasons explicitly rather than hiding them behind a score.

In this browser's storage (IndexedDB), on the device. It is built for megabytes, unlike the ordinary settings store where photographs would simply not fit. Clearing the site's data deletes the diary, so important shots are worth duplicating via the PDF export. In private mode the storage may be unavailable — the tool still works, but nothing survives a reload, and it warns you about that.

The tool compares the shooting conditions and warns when they diverged: a different reference, a noticeably different distance, flash used in one case and not the other. Such shots show a difference in lighting rather than in growth. The rule is simple: same spot, same distance, diffuse daylight, no flash — flash creates a highlight and flattens the relief.

Usually not, and that is fine. Ask someone or use a mirror — and note that a mirror image is reversed, which does not matter for measurement. What does matter is that the reference is in the same frame, and a mirror does not change its size.

No. It is a diary that makes the conversation concrete: instead of "I think it grew a bit" you bring dates, millimeters and a rate. It does not replace specialist screening — especially if you have many moles, fair skin, a history of sunburn or melanoma in the family.