Denier, Tex, Dtex, Nm and Ne: How Yarn Counts Convert
Yarn is described by how thick it is, but nobody measures thickness directly: a yarn is soft and squashes under a gauge. Instead, the textile trade describes yarn by its linear density, the relationship between its length and its mass. The trouble is that it does so in at least five different systems, and two of them run backwards from the others. A tights packet says 40 denier, a European data sheet says 167 dtex, a cotton shirt is "two-ply 80s", and a knitting yarn is labelled Nm 2/28. This guide explains each system, how they convert, and how to avoid the mistakes that come from mixing them, with every conversion run through the site's Denier / Tex / Dtex Yarn Count Converter.
Two families: direct and indirect
Direct systems give the mass of a fixed length. The bigger the number, the heavier and thicker the yarn.
- Tex: grams per 1,000 metres. The international standard system.
- Decitex (dtex): grams per 10,000 metres. Ten times the tex figure; common for synthetic filaments in Europe.
- Denier: grams per 9,000 metres. Traditional for silk and synthetic filaments, and still the norm for hosiery, outdoor fabrics and much of Asian and American trade.
Indirect systems give the length of a fixed mass. The bigger the number, the finer the yarn.
- Metric count (Nm): kilometres per kilogram, which is the same as metres per gram. Common for wool and many knitting yarns.
- English cotton count (Ne): the number of 840-yard hanks in one pound. The standard way to describe cotton and cotton-type spun yarns, especially for shirting and bed linen.
Because the two families run in opposite directions, the most common mistake in reading a yarn spec is assuming a bigger number means a thicker yarn when the system is indirect. Ne 80 is far finer than Ne 20.
The conversions
The converter routes everything through tex:
- tex = denier ÷ 9
- dtex = tex × 10
- Nm = 1000 ÷ tex
- Ne ≈ 590.5 ÷ tex
The Ne constant comes from the definition: a pound is 453.59 g and 840 yards is 768.1 m, and 453.59 ÷ 768.1 × 1000 is about 590.5. You will also see 590.6 or 590.54 quoted; the difference is far smaller than the variation between bobbins of real yarn.
Worked conversions
| Entered | Tex | Dtex | Denier | Nm | Ne |
|---|---|---|---|---|---|
| 15 denier | 1.67 | 16.67 | 15 | 600 | 354.3 |
| 40 denier | 4.44 | 44.44 | 40 | 225 | 132.86 |
| 75 denier | 8.33 | 83.33 | 75 | 120 | 70.86 |
| 150 denier | 16.67 | 166.67 | 150 | 60 | 35.43 |
| 167 dtex | 16.7 | 167 | 150.3 | 59.88 | 35.36 |
| 20 tex | 20 | 200 | 180 | 50 | 29.53 |
| 40 tex | 40 | 400 | 360 | 25 | 14.76 |
Notice the pair in the middle: 150 denier and 167 dtex are the same yarn to within rounding. Polyester filament sold as "150D" in one market is very often sold as "167 dtex" in another. Recognising that saves a lot of confusion when comparing suppliers.
Going from Ne or Nm to the direct systems
The converter takes denier, tex or dtex as input. To start from a cotton count or a metric count, turn it into tex first:
- from Ne: tex = 590.5 ÷ Ne. Ne 30 is 19.68 tex; Ne 40 is 14.76 tex; Ne 60 is 9.84 tex.
- from Nm: tex = 1000 ÷ Nm. Nm 28 is 35.71 tex.
Then enter the tex value. For Ne 40, entering 14.76 tex gives 132.86 denier, 147.63 dtex and Nm 67.74, and returns Ne 40 as a check. For Nm 28, entering 35.71 tex gives 321.43 denier and Ne 16.53.
Plied yarns: reading "2/60" and "60/2"
A plied yarn is two or more single yarns twisted together, and the notation for it is one of the most confusing parts of the subject because conventions differ between systems and trades.
- In the cotton and worsted trades, a count such as 2/60s or 60/2 usually means two single yarns of Ne 60 plied together. The resulting yarn has a resultant count of about Ne 30, because it is twice as heavy as one single.
- In the metric system, Nm 2/28 similarly means two singles of Nm 28 plied, giving a resultant of about Nm 14.
- In tex, the convention is often to give the single yarn tex and the number of plies, such as R 40 tex / 2, or simply the resultant tex.
Twisting the plies together shortens them slightly, an effect called twist contraction, so a metre of plied yarn weighs a little more than the sum of its singles and the resultant count is not exactly half the singles count. For everyday comparison the simple halving is close enough. When converting a plied count, work out the resultant first and convert that, not the singles figure, unless you specifically want the singles.
Filament counts: "75D/72F"
Synthetic filament yarns are often written with two numbers, such as 75D/72F. The first is the yarn's total denier; the second is the number of filaments in it. Dividing gives the denier per filament (dpf): 75 ÷ 72 is about 1.04 dpf. In dtex, 75 denier is 83.33 dtex, so each filament is about 1.16 dtex.
Two yarns of the same total denier can therefore feel completely different. 75D/72F has many fine filaments and is soft and drapey; 75D/36F has half as many, each twice as thick, at about 2.31 dtex per filament, and feels crisper. Microfibre fabrics are made from filaments at roughly 1 dtex or finer; definitions vary between countries and trade bodies, and some use 1 denier as the line instead. The guide to reading synthetic yarn specs goes further into this.
Where each system is used
- Denier: hosiery (tights from about 10 to 100 denier), outdoor and bag fabrics (70D, 210D, 420D, 1000D), silk, many filament yarns.
- Dtex: European synthetic filament data sheets, sewing threads, technical yarns.
- Tex: standards and technical specifications, sewing threads, glass and carbon rovings.
- Ne: cotton and cotton-blend spun yarns for weaving and knitting; the counts behind shirting and sheets.
- Nm: wool and wool-blend yarns, knitting yarns, linen in some markets.
Hand-knitting yarns are usually labelled by weight category (lace, fingering, DK, worsted, chunky) and by metres per 100 g. Metres per 100 g is really an Nm figure in disguise: 280 m per 100 g is Nm 2.8, or about 357 tex.
Measuring a yarn's count yourself
If you have a sample of yarn and an accurate scale, you can find its tex: measure a long length, weigh it, and divide grams by metres, then multiply by 1000. Ten metres weighing 0.2 g is 20 tex. Use as long a length as you can, because short samples on household scales give poor precision, and measure the yarn under light tension rather than stretched. Mills use wrap reels that wind an exact length, and condition the yarn before weighing.
Why the count matters
The count is the main thing that sets how fine, how heavy and how smooth a fabric made from the yarn can be. For woven fabrics, the yarn count together with the number of ends and picks per inch decides how densely the cloth is covered; the Thread Count & Cover Factor Calculator uses Ne counts for that reason. For knits, the count has to suit the gauge of the knitting machine. And for sewing threads, the count needs to match the needle size and the fabric weight.
What the converter does not cover
The converter is exact for the definitions above. It does not handle the older woollen and worsted counts, linen lea, or the various regional counts still used in particular trades, and it does not work out resultant counts for plied yarns: convert the resultant yourself first. Nor does a count say anything about fibre, twist, strength or evenness, which are separate properties on a full yarn specification. For a yarn that must meet a contract specification, the count should be measured on conditioned samples by a recognised method.