That Yarn · Journal
Cashmere Micron: What the Numbers Really Mean
Cashmere is measured in microns — but the number alone won't tell you whether a yarn is good. Here are the real figures, the second number that matters just as much, and why "Grade A" means less than you'd think.
Ask what makes cashmere good and almost everyone reaches for one number: the micron count. It is the right place to start, and it is genuinely important. But if you buy cashmere on micron alone, you can still end up disappointed — because fineness is only half of what decides how a cashmere yarn feels, wears, and lasts.
Here are the actual numbers, the second measurement almost nobody mentions, an honest word about the grading system, and how to read a cashmere blend.
What micron actually measures
A micron (or micrometre, µm) is a measure of fiber diameter — how thick a single strand of cashmere is. It does not measure length, softness, or quality directly. The lower the micron number, the finer the fiber, and the softer it generally feels against skin.
For scale: a human hair is roughly 50 to 100 microns across. Fine cashmere is well under 20 — often around a sixth the width of a hair. That extraordinary fineness is what gives cashmere its weightless softness and its warmth without bulk.
Very fine cashmere — about 14 to 16 microns
Good cashmere — about 16 to 19 microns
Coarse "cashmere" — above 19 microns, and increasingly prickly
In the US, the FTC defines cashmere as averaging 19 microns or less.
That FTC figure is worth holding onto: 19 microns is the legal ceiling, not the target. Anything at or below it may be sold as cashmere in the US — which means a fiber right at 19 microns and one at 14 microns are both, legally, "100% cashmere," while feeling very different indeed.
The second number almost nobody mentions
Here is the part that most cashmere writing leaves out, and it explains a great deal of disappointment. Micron is only one of two measurements that decide a cashmere's quality. The other is staple length — how long each fiber is.
Fineness determines how soft cashmere feels. Length determines how well it lasts. Long fibers can be spun into a stronger, more stable yarn with fewer loose ends, which means less pilling and better shape retention. Short fibers work loose, tangle, and pill — no matter how fine they are.
Which leads to a genuinely useful, counterintuitive rule: a very fine cashmere with short fibers will pill more than a slightly coarser cashmere with long fibers. If a seller quotes you a beautiful micron number and stays silent about staple length, you are only being told half the story.
Micron tells you how soft it will feel. Staple length tells you how long it will stay that way. A 14-micron cashmere with short fibers can pill faster than a 16-micron cashmere with long ones — which is why the number on its own proves nothing.
An honest word about "Grade A"
You will see cashmere sold as Grade A, B, or C, presented as though it were an official classification. It is worth knowing what that system actually is — and isn't.
There is no single, enforced industry standard behind those letters. Look across sources and the definitions contradict each other: one will define Grade B as 16 to 19 microns, another as 19 to 30; one puts Grade C above 19, another above 30. These are, in the main, descriptive conventions and marketing terms rather than a certified grading body's ruling. "Grade A" is a claim, not a certificate.
So use the letters as a rough orientation if you like — finer and longer is better, coarser and shorter is worse — but never let a letter stand in for a number. The reliable question is always: what is the actual micron count, and what is the staple length? A seller who knows their fiber will be glad to tell you both. A seller who deflects to "Grade A" and won't give figures is telling you something too.
| What you're told | What it's worth |
|---|---|
| "Grade A cashmere" | A marketing claim; no unified standard behind it |
| "100% cashmere" | True but broad — anything ≤19µm qualifies in the US |
| "Cashmere blend" | Meaningless without a stated percentage |
| "Cashmere feel" / "cashmere-like" | Not cashmere at all |
| "15.5µm, 36mm staple" | An actual specification — this is what to ask for |
How to read a cashmere blend — is 90/10 worth it?
One of the most common questions about cashmere is what to make of a blend: 90% wool, 10% cashmere, or similar. It is worth answering plainly, because the truth is neither "blends are a scam" nor "blends are just as good."
Blending is not automatically dilution. A blend can be a deliberate, intelligent choice: wool or merino adds elasticity, resilience, and pill resistance that pure cashmere lacks, while cashmere adds softness and warmth. A well-made merino-cashmere yarn can genuinely outperform pure cashmere for a hard-wearing garment, and cost far less. Silk-cashmere adds drape and sheen. These are real engineering decisions, not cost-cutting alone.
But be clear-eyed about what a small percentage does. At 10%, cashmere is a meaningful improvement to the hand — a softening of the surface, a gentler feel — rather than a transformation of the yarn's character. You are buying a wool yarn with a cashmere touch, not a cashmere yarn at a discount. Whether that is worth it depends entirely on the price and on the quality of the other 90%. A 90/10 blend of superb merino and fine cashmere can be a lovely yarn; a 90/10 blend of coarse wool and short-staple cashmere is just coarse wool with a marketing line.
A blend ratio without fiber quality tells you nothing. Ten percent fine, long-staple cashmere in a superb merino is a beautiful thing. Ten percent short, coarse cashmere in ordinary wool is a label. The percentage is the easy part to print.
The practical rule: a stated percentage is a good sign; a vague "cashmere blend" is a warning. If a yarn won't tell you how much cashmere is in it, assume the answer is "not much."
One common confusion: Cashwool is not cashmere
Worth clearing up, because the name misleads constantly. Cashwool contains no cashmere at all. It is a well-known extrafine merino wool — a superb fiber in its own right, at 19.5 microns or below — whose name simply evokes cashmere's softness. If you are buying Cashwool expecting cashmere, you are buying something else: excellent, but merino. We explain it fully in our guide to what Cashwool is.
Why cashmere is expensive — and why cheap cashmere exists
A single cashmere goat produces only around 150 to 200 grams of usable undercoat a year, hand-combed from beneath its coarse outer guard hair each spring. It can take the annual yield of several goats to make one fine garment. Add the painstaking work of de-hairing and sorting the finest fibers, and the price explains itself.
Which raises the obvious question: how can cashmere ever be cheap? Usually one of three ways. The fiber is coarse and short — technically cashmere, at the legal ceiling, and it will feel and wear like it. It has been heavily chemically softened, so it feels lovely in the shop and loses that softness after a few washes. Or it is a blend with very little actual cashmere in it. None of these is necessarily fraud; all of them are why the number, and the staple length, matter more than the word.
What to actually ask
Pulling it together, here is what separates an informed cashmere purchase from a hopeful one.
- Ask for the micron count. Under about 16 microns is genuinely fine; up to 19 is legally cashmere but increasingly ordinary.
- Ask for the staple length. Longer fiber means less pilling and a longer life. This is the question almost nobody asks, and it matters enormously.
- Treat "Grade A" as a claim, not a fact. Ask what number is behind the letter.
- Demand a stated blend percentage. "Cashmere blend" without a figure tells you nothing good.
- Feel it, then wash a swatch. Chemical softening flatters a fiber in the hand and washes out. A washed swatch is the honest test — as it is for every yarn, and doubly for cone yarn.
And remember the wider principle, which cashmere illustrates better than almost any fiber: consistency matters as much as any average. Softness against skin depends less on a fiber's mean micron than on the proportion of coarser fibers mixed in — a point our guide to micron and comfort factor works through in full. The finest fiber, poorly sorted, can prickle.
The short version
Cashmere micron measures fiber diameter: very fine cashmere runs about 14 to 16 microns, good cashmere 16 to 19, and the US FTC's legal ceiling for calling something cashmere is an average of 19 microns or less — a ceiling, not a target. But micron is only half the story: staple length decides durability, and a very fine cashmere with short fibers will pill faster than a slightly coarser one with long fibers. "Grade A" has no single enforced standard behind it, so ask for actual numbers instead. And a blend percentage means nothing without knowing the quality of the fiber it describes. Ask for the micron, ask for the staple length, insist on a stated percentage — and wash a swatch before you believe any of it.
Frequently asked questions
What is the micron count of cashmere?
Cashmere fiber diameter typically ranges from about 14 to 19 microns. Very fine cashmere is around 14 to 16 microns; good cashmere sits around 16 to 19. In the US, the FTC defines cashmere as averaging 19 microns or less, which is a legal ceiling rather than a quality target — a 19-micron fiber and a 14-micron fiber can both be sold as 100% cashmere while feeling very different.
What is the fiber diameter of cashmere in micrometers?
The same thing: a micron and a micrometre (µm) are the same unit. Cashmere fiber diameter is roughly 14 to 19 µm. For comparison, a human hair is about 50 to 100 µm across, so fine cashmere is around a sixth the thickness of a hair — which is what gives it such softness and warmth without weight.
Does a lower micron always mean better cashmere?
No — micron is only half of it. Staple length (how long each fiber is) matters just as much, because long fibers spin into a stronger yarn with fewer loose ends, which resists pilling and holds shape. A 14-micron cashmere with short fibers will pill faster than a 16-micron cashmere with long fibers. Consistency matters too: the proportion of coarser fibers mixed in affects prickle more than the average does.
Is "Grade A" cashmere an official standard?
No. There's no single, enforced industry standard behind Grade A, B, and C — definitions contradict each other across sources, with one calling 19 microns Grade B and another Grade C. They're descriptive and marketing conventions, not a certification. Treat "Grade A" as a claim, and ask for the actual micron count and staple length instead.
Is 90% wool 10% cashmere worth it?
It depends entirely on the quality of both fibers. At 10%, cashmere improves the hand — a softer surface and gentler feel — rather than transforming the yarn; you're buying a wool yarn with a cashmere touch, not discounted cashmere. A 90/10 blend of superb merino and fine cashmere can be a lovely, hard-wearing yarn that outperforms pure cashmere for durability. The same ratio with coarse wool and short cashmere is just coarse wool. The percentage alone tells you nothing.
Is Cashwool the same as cashmere?
No — Cashwool contains no cashmere at all. It's a well-known extrafine merino wool, at 19.5 microns or below, whose name simply evokes cashmere's softness. It's an excellent fiber in its own right, but if you're buying it expecting cashmere, you're buying merino.
Some yarns don't come back.
That Yarn drops new mill-end on the 1st and 15th.
Have a question about a specific cone? Write to us at hello@thatyarn.com — we answer every email.
