Yarn Count Converter

tex, decitex, denier, Nm, Ne, worsted, linen lea and the woollen counts, all in one place — with the inversion made obvious, because the direct systems go up as the yarn gets thicker and the indirect ones go down. Treat them alike and your answer is not slightly wrong, it is upside down.

One reciprocal, and eight constants

The nine systems, and which way each runs

Where the constants come from

One yarn, every count

Plied yarns, and what the notation does

Two opposite ways to measure one yarn

Yarn is measured in two families and they run in opposite directions. A direct count is a mass per unit length: tex is the grams in a kilometre, decitex the grams in ten kilometres, denier the grams in nine kilometres. Bigger number, thicker yarn. An indirect count is a length per unit mass: Nm is metres per gram, Ne the number of 840-yard hanks in a pound, worsted count the number of 560-yard hanks, the linen lea 300-yard hanks. Bigger number, thinner yarn. So every conversion between the two families is a reciprocal, and if you add where you should divide you do not get a slightly wrong answer — you get one that is upside down. A 40s cotton is finer than a 20s. A 40 tex is coarser than a 20 tex. Both sentences are true and they are about the same direction of change.

The arithmetic is trivial once the direction is settled. tex = denier ÷ 9. Nm = 1000 ÷ tex. Every indirect system is K ÷ tex for a constant K that comes from its own hank length: K is the grams in a pound divided by the metres in a hank, so cotton’s 840-yard hank gives 453.59237 × 1000 ÷ (840 × 0.9144) = 590.5412, which is the 590.5 every textbook prints and the 591 Cotton Incorporated rounds it to. Worsted’s 560-yard hank gives 885.81; the linen lea’s 300 yards give 1653.5. None of those numbers is remembered on this page — they are computed from the hank lengths and the exact pound and yard, and the two that a nameable publisher prints are the check.

One shortcut worth memorising: Nm ÷ Ne = 1.6934, for every yarn there has ever been, because both are a constant over tex. Multiply a cotton count by about 1.69 and you have the metric count. Divide by 1.69 to go back.

Plying is where people go wrong next. A cone marked 2/60s — or 60/2, depending on which side of the Atlantic printed it — is two 60s singles twisted together, and the resultant yarn is a 30s: twice as thick as its singles, so half the count. In the direct family the same fact reads more naturally, because direct counts simply add: two 20 tex singles make a 40 tex plied yarn. The general rule for indirect counts is 1/N = 1/N₁ + 1/N₂ + …, which for equal singles is just N ÷ n. And the notation itself is a trap: the American convention writes singles over plies, so 8/2 cotton is two plies of 8s, while several other countries write the numbers the other way round and call the same yarn 2/8. Warped Fibers gives the grist arithmetic for the American form — base hank × singles ÷ plies — and an 8/2 cotton comes out at 840 × 8 ÷ 2 = 3,360 yards to the pound. If you have any choice, write the resultant tex and the ply count and let the notation argument go.

What this page cannot tell you. A count is a linear density, not a thickness. Two yarns at the same tex in different fibres, or at different twist levels, are physically different diameters, because the fibre density and how tightly the yarn is packed both matter and neither is in the count. This page therefore gives no yarn diameter at all: doing so would need a fibre density and a packing factor, and inventing either would be worse than leaving the row out. What it does give is a relative thickness figure — the square root of tex, since mass per length goes as area — which is honest about being a comparison rather than a measurement. For the needles the yarn goes onto, and another scale that runs backwards for the same historical reason, see the needle gauge converter; for the wire gauges that started the habit, the wire gauge converter. This page does the arithmetic. Where the answer carries a consequence — a dose, a structural load, a legal area, a medical measure — confirm it against the authority that governs it before relying on it.

Frequently asked questions

Related calculators

References

1. Cotton Incorporated, technical bulletin TRI-1014, Yarn Numbering Systems (read 26 September 2026): tex is the mass in grams of 1,000 m and denier the mass of 9,000 m; cotton count is 840-yard hanks per pound and worsted count 560-yard hanks; the rounded conversion constants are 591 for cotton count and 5,315 for denier; direct counts add when yarns are plied and indirect counts combine as the sum of their reciprocals.
2. Textile School, Yarn Count Conversions (read 26 September 2026): the hank lengths behind each indirect system — 840 yd for English cotton, 560 yd for worsted, 300 yd for the linen lea, 1,000 m per kilogram for the metric count — and the 590.5 ÷ tex form of the cotton conversion.
3. Warped Fibers, Your Guide To Decoding Weaving Yarn Sizes (read 26 September 2026), for the plied notation: the American convention writes singles over plies, so 8/2 cotton is two plies of 8s and runs 840 × 8 ÷ 2 = 3,360 yards to the pound, while several other countries write the two numbers the other way round, making a 2/8 abroad an 8/2 in the States.