Yarn Count Converter

Yarn count is where most knit specifications go wrong, and the reason is simple: there are two families of count systems that run in opposite directions, and the most common pair — English cotton count and metric count — differ by a factor of 1.69. Enter any one value below and the converter fills in the rest. Below it, the formulas, the constants, and the mistakes worth avoiding.

Two Families Running in Opposite Directions

Every yarn count system is either indirect or direct, and knowing which family a number belongs to tells you instantly which way it scales.

Indirect counts measure length per unit of weight — Ne, Nm and worsted count. A higher number means more length for the same weight, so a higher number means a finer yarn. Ne 40 is finer than Ne 20.

Direct counts measure weight per unit of length — Tex, dtex and Denier. A higher number means more mass for the same length, so a higher number means a thicker yarn. 300 denier is heavier than 150 denier.

Getting these backwards is the single most common specification error in knit sourcing, and it produces a fabric that is either twice as heavy or half as heavy as intended.

The Constants You Need

The constant 590.54 comes from the definition of the English cotton count: the number of 840-yard hanks in one pound. Work it through — 840 yards is 768.096 metres, one pound is 453.592 grams, and 1000 × 453.592 ÷ 768.096 gives 590.54. You never need to memorise that derivation; you only need the constant.

The 1.69 Trap

Ne and Nm are both indirect counts, which makes them easy to confuse, and they differ by a factor of about 1.69. Ne 30 is Nm 50.8 — not Nm 30. If a supplier writes “30s” without saying which system, you are looking at a fabric that could be either 30s cotton count or 30s metric, and those are very different yarns: Nm 30 is roughly Ne 17.7, close to twice as thick.

The same trap exists between denier and dtex, which differ by only 1.11. That one is less dramatic but still enough to shift hand feel on a fine filament knit. Always write the unit next to the number in your specification. Never write just a number.

Quick Reference

Why Spun Yarn Uses Ne and Filament Uses Denier

The split is historical and it is still almost universal. Staple spun yarn — cotton, polyester spun, blends — is irregular in cross-section, so it is quoted in an indirect count that describes how much length you get per pound of a naturally varying strand. Filament yarn is continuous and uniform, so it is quoted directly by mass per length, and additionally by filament count: 75D/72F means 75 denier made up of 72 individual filaments.

That filament count matters more than beginners expect. Two polyester yarns both at 75 denier feel completely different if one is 36 filaments and the other is 144. More filaments at the same total denier means each filament is finer, and the resulting fabric is softer and drapes better.

Relating Count to the Fabric You Get

Count alone does not determine GSM; machine gauge and stitch length do. But as a working guide on a standard single-jersey machine, coarser yarn gives heavier fabric: 20s to 26s lands in fleece and heavy jersey territory, 30s sits at the heart of standard tee production, and 40s and finer produces the smooth, dense surface buyers associate with premium retail jersey.

If you are specifying both a count and a GSM, check that they are compatible. Asking for 180 GSM from 20s yarn on a fine-gauge machine, or 240 GSM from 60s yarn, will send the mill back to you with questions.