Reading the signs
The ponytail test: the one measurement that tells you the truth
If you do one thing from this site, do this. It costs nothing, takes a minute, and it is the measurement I trust more than any photograph.
Why the ponytail
The circumference of the ponytail at its base is a direct measure of the total volume of hair on the head: the number of hairs multiplied by their thickness. It captures the two things that matter — whether follicles are producing hair, and how thick that hair is — and it ignores the things that fool the eye: length, colour, how you have combed it, the light in the bathroom. Trichologists use it in clinic because it is more reliable than looking.
How to do it
Dry hair, not freshly washed and not full of product; the day after a wash is ideal. Brush through. Gather all of it into a low ponytail at the nape, as you normally would, and secure it with a bobble. Take a soft dressmaker’s tape — not a ruler — and wrap it once around the ponytail just below the bobble, snug but not tight. Read the number in centimetres, to the nearest half. Write it down with the date.
Do it once a month, same conditions, same place on the ponytail. A single reading tells you nothing; three readings tell you the direction.
Not sure which one is you?
Take the two-minute hair quiz
Twelve quick questions. We tell you what we think is going on, what to do about it, and we say so if it is something we cannot help with.
Start the quiz →What the numbers mean
A ponytail of around 10 cm circumference is on the fuller side; 7 to 9 cm is average for a woman with fine to medium hair; under 6 cm is thin. But the absolute number matters far less than the trend. A fall of half a centimetre over three months is real thinning. A stable number over six months means whatever is happening has stopped. A rise of half a centimetre means more hairs, thicker hairs, or both — and it is the first objective sign that a treatment is working, typically four to five months in, before the mirror agrees.
What it cannot tell you
Where. A ponytail can hold steady while the temples recede, because the temples contribute little to it. Pair it with the parting photograph — the protocol is here — and you have both the amount and the place.
Why. A falling number does not tell you whether it is a shed, miniaturisation, breakage or a thyroid problem. It tells you to find out.
Why the number matters emotionally
Women who thin after children tend to spend years in a fog of not knowing: it looks fine, then terrible, then fine. That fog is exhausting. A number ends it. If it is falling, you have a reason to act and a way to know when the action is working. If it is stable, you can stop checking the mirror every morning. Either way it is better than not knowing, and it takes one minute a month.
Ready to read your own pattern?
Take the two-minute hair quiz
Twelve questions. We tell you what we think is going on for you, and we say so if it is something a GP should see first.
Start the quiz →
