Articolo: Hair Density: What It Is, How to Check It and How to Care for It
Hair Density: What It Is, How to Check It and How to Care for It
Hair density is how many hairs grow on each square centimetre of your scalp. It is not the same as how thick each strand is. This guide explains what hair density means in the numbers studies report, how to check yours at home, where the published bands disagree, and how care differs for low, medium and high density.
What is hair density?
Hair density is a count of the hairs on a patch of scalp, which studies report in hairs per square centimetre (hairs/cm²).
The values depend on who was measured, where and how. A 2001 study of 377 women at a UK dermatology clinic, measured with a photographic method, found an average of 293 hairs/cm² at age 35, falling to 211 hairs/cm² at age 70. A 2018 study of three groups of healthy adults in the United States found averages between 148 and 230 hairs/cm² across the groups and three scalp areas. In a 2001 study of 38 young adults from central and western Africa, individual values ranged from 90 to 290 hairs/cm² within that one group. Published averages disagree, and the spread between people is wide.
In the 2001 clinic sample, density followed a normal bell curve, running smoothly from few to many hairs. The labels low, medium and high are therefore cut points chosen by guides, not natural types.
Density also varies across the head and with age. A 2016 study of 2,249 young adults from 24 ethnic groups found differences linked to scalp area and geographic origin, and the studies cited here do not agree on one densest area. Studies in the UK, Korea and Thailand found density lower in older age groups, and in a 2012 study of 1,099 Caucasian women who felt their hair was thinning and 315 who did not, density measured by phototrichogram was highest between 20 and 30. No pillowcase, bonnet or routine makes a strand thicker, and no care product makes it permanently thicker or adds more strands.
Hair density vs hair thickness
Density is how many strands you have; thickness is how wide each strand is. Adult hairs are about 20 to 180 micrometres (µm) wide, and one study marked a thick hair as over 80 µm and a vellus hair, the very fine kind, as under 40 µm. We found no agreed cut-offs for fine, medium and coarse, so those words describe a relative scale. What fine strands mean for washing, brushing and styling is covered in our guide to fine hair.
The two get mixed up. In a 2016 study of 151 women, what they called “fine hair” covered density, strand thickness, strength and the volume of hair on the head. A common home check for strand width is to roll a single shed hair between your fingertips: if you can barely feel it, it is usually counted as fine; if you can clearly feel its texture, as medium or coarse. How fine strands and low density play out in curls is covered in our guide to thin curly hair. Density and thickness often combine like this:
| Low density | High density | |
|---|---|---|
| Fine strands | Scalp shows easily; hair feels light | Scalp hard to see; hair is weighed down easily |
| Coarse strands | Strands feel wiry; scalp shows easily | Scalp hard to see; hair feels heavy and, according to hair care guides, dries slowly |
How full your hair looks depends on both. The same 2012 study found that neither density nor strand width alone explained how much hair the women felt they had.
Hair density test: how to check your hair density at home
Knowing how to check hair density at home comes down to looking at your scalp and measuring a ponytail, then reading both with the strand check above. None of these gives a density figure; they sort you roughly into a band.
The parting check
Look at your roots in a mirror, in daylight, with your hair dry and loose, and check the parting, the crown and the sides. One hair guide reads it this way: if you can see your scalp easily without parting the hair, density is low; if you have to part it to see skin, it is medium or high.
The ponytail check
Gather dry hair into a ponytail and measure round its base with a flexible tape. The table shows the bands published by these sites.
| Site | Ponytail position | Low | Medium | High |
|---|---|---|---|---|
| Healthline | Not stated | Under 5.1 cm (2 in) | 5.1 to 7.6 cm (2 to 3 in) | 10.2 cm (4 in) |
| Curlsmith, Verb | Low | Under 5.1 cm (2 in) | 5.1 to 7.6 cm (2 to 3 in) | Over 10.2 cm (4 in) |
| Ethique | Not stated | Under 5.1 cm (2 in) | 5.1 to 7.6 cm (2 to 3 in) | Over 10.2 cm (4 in) |
| HairGP | At the crown | Under 5 cm (about 2 in) | 5 to 10 cm (about 2 to 4 in) | Over 10 cm (about 4 in) |
| FIA system, via Wikipedia | Not stated | Under 5.1 cm (2 in), called “thin” | 5.1 to 10.2 cm (2 to 4 in), called “normal” | Over 10.2 cm (4 in), called “thick” |
Four of the sites (the first three rows) give no band for 7.6 to 10.2 cm (3 to 4 in), and the sites differ on where to tie the ponytail. Our reading: under about 5 cm is low, over about 10 cm is high, and between about 7.5 and 10 cm the sources disagree. The ponytail check also picks up strand thickness, and it only works if your hair is long enough to tie back.
Putting the checks together
Use all three checks together. If they disagree, treat the parting check as the density check, because the ponytail mixes in strand thickness. It is easy to be unsure whether you are medium or high: the bands are conventions, and the checks are rough.
How a dermatologist measures it
In a clinic, hairs are counted on magnified images of a small patch of scalp, using trichoscopy or a phototrichogram, or by plucking the hairs from a small measured area. Even the professional methods differ: in a 1993 study, a phototrichogram and a plucked count on the same 12 people gave averages of 181 and 237 hairs/cm². A measurement like this is only needed when there is a medical question.
Low, medium and high density hair: care and styling
Density is usually tied to how much product your hair needs, how long it takes to dry and how it is best cut.
Low density hair
Use less, lighter product and keep it off the roots. On cuts, guides disagree: some advise blunt lines and few layers, others a highly layered shag. Stylists' reasoning explains the split: layers take out bulk and blunt ends keep weight, so on low density hair, stylists keep layers light, because heavy layers can look stringy. Handle it gently.
Medium density hair
General hair care advice fits medium density well; strand thickness and curl pattern decide the details, such as how heavy a product to use.
High density hair
High density hair usually needs more product to cover it and often takes longer to dry. When drying or styling, work in more and smaller sections, starting at the nape with horizontal rows about 2.5 to 5 cm (1 to 2 in) thick and working up towards the crown. Detangle section by section as well, as set out in our guide on how to detangle curly hair. Layering can take out some of the bulk.
On product weight, guides disagree again: some suggest volumising, lightweight products, others heavier creams, gels or smoothing formulas. Our reading: the lighter advice suits fine, dense hair and the heavier advice coarse, dense hair.
In dense or long hair, the weight of the hair pulls on the ponytail. Wear it loosely tied; two loose ties instead of one tight one are one way to do that. How to choose and wear a gentle tie is covered in our guide to hair ties that do not damage hair. Change where you tie it from day to day, so the same hairs are not pulled every time.
Density, porosity and curl pattern
Density, porosity and curl pattern are three separate properties. Density is a count of hairs on the scalp. Porosity is a property of each strand: how readily it takes up water; laboratory studies measure it on the fibre itself, and a hair porosity test gives a rough idea of yours. Curl pattern is the shape each strand takes, sorted in charts of curly hair types. A routine that suits your hair takes all three into account.
Friction and handling
Rubbing wears hair a little at a time. A 2015 review of hair cosmetics names the friction of everyday grooming as one cause of that wear, and at night your hair rubs against the pillowcase each time you turn over. On friction, silk usually has the edge: its smooth, dense surface creates less friction against hair than a cotton weave does. A pillowcase does not change how many hairs you have, and it does not repair damaged hair.
What a smooth pillowcase can and cannot do is set out in our guide to silk pillowcase benefits. Between washes, tie your hair loosely, and if it is curly, work knots out with your fingers on damp hair, or on fully wet hair if the curls are fine, rather than with a comb on dry hair; both reduce pulling on it.
What your hair density cannot tell you
A home density check describes how much hair you have, not whether it is changing. It is normal to shed between 50 and 100 hairs a day. Hair that has become noticeably thinner, or falls out suddenly, is a question for a doctor.
What our silk pillowcases are made of
Our silk pillowcases are 100% organic mulberry silk at 22 momme and Grade 6A. Both faces are silk, and a hidden YKK zip closes each case. Their silk is GOTS certified. The pillowcases carry the OEKO-TEX MADE IN GREEN label, and the label ID M27MNB1V9 can be checked on the OEKO-TEX website. The pillowcases carry the Dermatest 5-Star seal and the Dermatest Sensitive Skin seal, dermatologically tested for sensitive skin.
Frequently asked questions
What is hair density?
Hair density is how many hairs grow on each square centimetre of your scalp. Averages differ widely between studies, for example from about 134 hairs/cm² (Thai adults, side of the scalp) to 293 (UK women aged 35), depending on the group, scalp area and method.
What does hair density mean for my hair care?
Hair density mostly shows in how much product your hair needs, how long it takes to dry and how it is best cut. Low density means less, lighter product and light layers at most; high density usually means more product, often more drying time and smaller sections.
How do I check my hair density?
To check your hair density, look at your scalp with your hair dry and loose. One hair guide reads it this way: if you can see your scalp easily without parting the hair, density is low; if you have to part it to see skin, it is medium or high. A ponytail and a strand check add detail, but none gives a density figure.
Is high density hair the same as thick hair?
No, high density means many strands, while thick often means wide strands, and the two vary separately. Fine strands can grow densely and coarse strands can grow sparsely, which is why “thick hair” can mean either.
Does hair density change with age?
Yes, in the studies above hair density tends to fall from the 20s on. In one UK clinic sample of women, the average fell from 293 hairs/cm² at 35 to 211 at 70.
Sources
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- Robbins C et al., What women want: quantifying the perception of hair amount (2012): PubMed
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- Loussouarn G, African hair growth parameters (2001): PubMed
- Birnbaum et al., Evaluation of hair density in different ethnicities in a healthy American population using quantitative trichoscopic analysis (2018): PMC
- Leerunyakul and Suchonwanit, Evaluation of hair density and hair diameter in the adult Thai population using quantitative trichoscopic analysis (2020): PMC
- Bouabbache S et al., What is a Caucasian “fine” hair? (2016): PubMed
- Kim JE et al., Phototrichogram analysis of normal scalp hair characteristics with aging (2013): PubMed
- Ishino A et al., Contribution of hair density and hair diameter to the appearance and progression of androgenetic alopecia in Japanese men (2014): PubMed
- Yang, Zhang and Meyers, The structure of people's hair (2014): PMC
- Rushton DH et al., Comparative evaluation of scalp hair by phototrichogram and unit area trichogram analysis within the same subjects (1993): PubMed
- Gavazzoni Dias, Hair cosmetics: an overview (2015): PMC
- American Academy of Dermatology, Do you have hair loss or hair shedding? (accessed September 2026): AAD
- NHS, Hair loss (2024): NHS
- Wikipedia, Hair (accessed September 2026): Wikipedia
- Healthline, What is hair density and how can I determine mine? (2020): Healthline
- Curlsmith, Hair density: meaning, identify and care: Curlsmith
- Verb, What is hair density? A guide to caring for thick vs. thin hair (2025): Verb
- Ethique, Hair density: how to measure and care for your type (2025): Ethique
- HairGP, Hair density guide: identify, manage and treat (2026): HairGP
RENESSY · Updated September 2026