Coarse Hair: What It Is, How to Tell and How to Care for It

Coarse hair means each strand is wide: the word describes the width of a single hair, measured as its diameter, not how much hair you have. Where coarse begins differs from study to study. Wide strands tend to hold a set, a styled shape, longer than narrow ones; most care advice is agreement among guides, not the result of studies.

What is coarse hair?

Coarse hair is hair in which each strand is wide. Strand width is the diameter of a single hair, usually given in micrometres (µm), thousandths of a millimetre. When people speak of coarse hair texture, texture means this width, although the word is also used for curl pattern.

Coarse is not the same as rough. Hair that has turned rough or wiry after heat styling or chemical treatments is damaged, and a damaged fine strand is still fine. The word “wiry” is used for naturally coarse hair and for damaged hair, and our guide to what damaged hair looks like describes heat-damaged hair as dry, rough and wiry.

Curl is a separate property too. A 2023 review reports that straighter hairs tend to be round with a larger cross-section, the area you would see if you cut straight across the strand, and curlier hairs oval with a smaller one. Wavy or tightly curled hair is therefore not necessarily coarse, and “coarse curly hair” names two properties at once. Curl patterns are covered in our guide to curly hair types.

Coarse, medium and fine: where the line falls

A 1978 salon study of 49 heads grouped hair as fine at 40 to 60 µm, medium at 60 to 90 µm and coarse at 90 µm or above, and its authors describe 90 µm as an arbitrary point. A 1977 study called a group of hairs averaging 89 µm coarse, as judged against the hair of adult American women of Caucasian origin. A 2014 study of 369 Japanese men counted hairs over 80 µm as thick, and a 2020 paper, citing earlier work, lists hairs over 66 µm as thick. A hair 70 µm wide is therefore medium by the 1978 grouping, thick by the 2020 list and not thick by the 2014 line. We found no agreed cut-offs for fine, medium and coarse, so those words describe a relative scale. Our guide to fine hair covers the narrow end of that scale.

Width differs between groups of people on average, and widely within them. Asian hair comes out wider in two sources: a 2020 review of Asian hair reports a larger cross-section for it than for African or Caucasian hair, and a 2016 study of young adults from 24 ethnic groups, which recorded diameter where it was practical, reports a larger diameter for Asian hair. A 2019 study of 257 Mexican women found a large spread in every hair property it measured, width included, both between people and within one person's hair. Width also shifts with age: in a 2012 study of more than 1,400 Caucasian women, most of whom felt they were losing hair, scalp hair width rose from age 20 until about 40 to 45 and then fell, and a hair science reference book puts the peak for men at about age 20.

Coarse hair vs thick hair

Coarse hair describes the width of each strand, while “thick hair” is used both for wide strands and for a lot of strands. In this guide, coarse refers only to width. Strictly, strand width and strand count are two different measures. Density is how many strands you have; thickness is how wide each strand is. Both shape how much hair you seem to have: in the 2012 study of Caucasian women, neither the fall in density nor the change in strand width alone fully accounted for the women's sense that they had less hair. How density is counted is covered in our guide to hair density.

How to tell if your hair is coarse

A common at-home check is to roll a single shed hair between your fingertips: if you can barely feel it, it is probably fine; if it feels like a sewing thread, it is probably medium or coarse. The check tells fine hair from hair that is not fine, but it cannot separate medium from coarse, and the three-tier sewing-thread scales found online give no source for their lines. Try hairs from a few places on your head, since width varies within one person's hair. Drying time is not a reliable test of width: we found no study that timed drying by strand width, and length, density and the air in the room affect it. How long a style lasts is no reliable test either, since it depends on more than width.

Why coarse hair holds a style

Coarse hair tends to hold a set longer than fine hair because a wide strand resists bending far more than a narrow one. A 1985 study puts it simply: in the absence of other stabilising factors, a fine hair 50 µm wide has only a fifth of the styling stability of a hair with what the authors call a “normal” width of 75 µm. In the 1977 study, which tested hair that had first been bleached and chemically straightened, tresses held a set better as strand width rose, up to the group it called coarse, although the wider hairs kept more small bends after that straightening, and its authors add that any effect of those bends is unknown. A 1967 study found no real difference in the stiffness of the material, known as its modulus, between coarse and fine hairs from the same batches: a fine hair simply has less material to resist a load. In moist conditions, the fine hairs in that study also crept, that is, slowly gave way under load, and did so clearly faster than the coarse ones. In a photograph in the same study, curls set in the coarsest hair, dried and then hung up, stayed shorter and tighter than curls set in the finest.

A wide strand has more material across it, so it is likely to take more force to snap. That is our inference from two sources. In a 2024 study of hair mechanics, stress means the force on a strand per unit area of its cross-section, so a wide strand spreads the same pull over more material. In the same 2020 paper that lists the 66 µm line, stretched hairs broke where they were narrowest. Any extra force would come from the extra material, not from better material: a 2020 study of hair from eight species, people included, found tensile strength, the stress a hair can bear before it breaks, generally lower in wider hairs. We found no study that measured breaking force by hair width. The closest measured result we found is an abrasion test in the 1977 study that imitates combing and brushing, run on the same bleached and straightened hair in tresses with the same number of hairs: tresses of the 89 µm group lasted nearly twice as many cycles as those of the 65 µm group.

Is coarse hair dry or frizzy?

Many guides describe coarse hair as dry or prone to frizz; we found no study that links either to strand width. Dryness is a condition of the hair, while width is a property of each strand. If your hair feels dry, our guide to dry hair covers the causes.

A 2024 review restates its author's earlier proposal to define frizz as hair failing to line up neatly, or partly losing that alignment after styling. What sets frizz off, from humidity to static, is covered in our guide to frizzy hair.

Hair care guides agree that thick, coarse strands dry more slowly than fine ones; we found no study that timed the difference. Length, density and the air in the room also play a part, as our guide to why your hair takes so long to dry explains.

How to care for coarse hair

Most guides suggest conditioner on the mid-lengths and ends, and more of it than for fine hair. Very fine hair only takes a little oil before it hangs heavy; thick and curly hair usually takes more.

Guides disagree on detangling: some advise brushing coarse hair while wet, others warn that combing damp hair may do more damage than combing it dry. Either way, most suggest working gently, a section at a time, from the ends upwards. Many guides also suggest lower heat settings on dryers and styling tools.

Most guides suggest regular trims, at intervals that differ from guide to guide and are given without a source. A split or snapped strand cannot be restored: care products can only hold a split together or smooth it down for a while, and the lasting fix is to cut it off.

Coarse hair at night

Most guides suggest going to bed with hair that is no longer wet. Whenever you turn over in your sleep, your hair rubs against the pillowcase. 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 repair hair that is already damaged.

What care cannot do

We found no agreed cut-offs for fine, medium and coarse, no study that timed drying by strand width and no study that links dryness or frizz to width. Care works with the hair you have. Average strand width changes only gradually over the years.

What our silk pillowcases are made of

The RENESSY silk pillowcases use 100% organic mulberry silk with a weight of 22 momme, and both faces of each case are silk. Mulberry silk comes from silkworms raised on the leaves of the mulberry tree, and momme measures the weight of silk fabric. The raw silk is rated grade 6A, the top class in the Chinese raw-silk standard (GB/T 1797). GOTS, the Global Organic Textile Standard, certifies textiles made from organically grown fibres. The silk is GOTS certified. OEKO-TEX MADE IN GREEN is a label for textiles tested for harmful substances and made in traceable, certified production. 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. A hidden YKK zip closes each case.

Frequently asked questions

What is the difference between coarse hair and thick hair?

Coarse hair describes the width of each strand, while “thick hair” is used both for wide strands and for a lot of strands. Strictly, strand width and strand count are two different measures. Density is how many strands you have; thickness is how wide each strand is.

How can you tell if your hair is coarse or fine?

Rolling a single shed hair between your fingertips tells fine hair from medium or coarse hair: if you can barely feel it, it is probably fine, and if it feels like a sewing thread, it is probably medium or coarse. Touch cannot separate medium from coarse, so treat the result as a rough guide.

Does coarse hair hold a style better than fine hair?

Coarse hair tends to hold a set longer than fine hair because a wide strand resists bending far more than a narrow one: a 1985 study put the styling stability of a 50 µm hair at a fifth of that of a 75 µm hair, other stabilising factors aside. In a 1977 study of hair that had first been bleached and chemically straightened, tresses held a set better as strand width rose, up to a group averaging 89 µm that its authors called coarse, though the wider hairs were left with more small bends after that straightening, and the authors call any effect of those bends unknown.

Is coarse hair always dry?

Coarse hair is not dry by definition: dryness is a condition of the hair, coarse describes strand width, and we found no study that links dryness to width. On drying time, hair care guides agree that thick, coarse strands dry more slowly than fine ones; we found no study that timed the difference.

Sources

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