Yarn Count Systems on Machinery Spec Sheets: tex, dtex, Denier, Ne and Nm

Two families that run in opposite directions

Count systems split into two groups. ISO 1144 calls them direct and indirect.

• Direct systems give mass per unit length. The bigger the number, the thicker the yarn. Tex is grams per 1,000 m, decitex (dtex) is grams per 10,000 m, and denier is grams per 9,000 m.
• Indirect systems give length per unit mass. The bigger the number, the finer the yarn. Metric count (Nm) is kilometres per kilogram, which is the same as metres per gram. English cotton count (Ne) is the number of 840-yard hanks in one pound. Worsted count uses 560-yard hanks per pound, and linen lea uses 300-yard leas per pound.

ISO 1144 makes tex the universal system, with millitex, decitex and kilotex as recommended units. Catalogues still mix systems: cotton machinery is usually quoted in Ne, filament machinery in dtex or denier, worsted machinery in Nm. Linen has its own lea count, which matters if you are pricing a line like the listed flax preparation and spinning family, from hackling to wet-spinning frames.

Conversion constants you can rely on

The appendix to ISO 1144 lists factors and constants to four significant figures. The figures below match those tables and the unit definitions (1 lb = 453.59237 g, 1 yd = 0.9144 m).

Two useful relationships follow from these. Denier equals 0.9 × dtex, so 150 denier is 166.7 dtex. Ne equals 0.5905 × Nm, so Nm 50 is about Ne 29.5. Trade tables often round 590.5 to 590 or 591. The difference is under 0.1 %. That is irrelevant for machine selection but can matter when you check a test report against a contract tolerance during a factory acceptance test.

Worked conversions

Ply and filament notation

The trade writes plied yarn as a count and a number of plies separated by a slash, but the order is not fixed. Cotton spinners often write 2/40s or 40/2 for two Ne 40 singles twisted together. Metric and worsted users more often write Nm 50/2. In an indirect system the nominal resultant count is the single count divided by the number of plies, so 2/40s behaves roughly like Ne 20. In a direct system you multiply, so 2 × 14.76 tex gives about 29.5 tex. The machines that make these yarns, two-for-one twisters, direct cablers and doublers, are usually quoted by the count of the singles they are fed.

That figure is nominal. ISO 858 describes the formal tex notation for plied and cabled netting yarns: single linear density × folds, then "R" with the resultant linear density, then the final twist direction. Its own example is 23 tex × 6 × 3; R 460 tex Z. The 18 components add up to only 414 tex. The standard explains that the extra 46 tex comes from the take-up caused by twisting and cabling. That is one more reason to state the twist level and direction alongside the count. ISO 1139 (revised 2025) gives the general designation rules, including filament number and twist.

Filament yarns are written as a total count plus a filament number, for example 150D/48F or dtex 167 f 48. Here 150 denier is the whole bundle. Each filament is 150 ÷ 48 ≈ 3.1 denier, or about 3.5 dtex. Machines can limit filament fineness as well as total count, so quote both. This matters most on texturing and covering machines. The listed YQ800DS draw-texturing machine, for example, is described for processing POY into polyester DTY, and both of those yarns are specified by total count and filament number.

Reading a range such as "20–3500 dtex" or "2–140 S/2"

A brochure range means nothing until you know the count system, whether it is input or output count, and whether it applies to singles or plied yarn.

• 20–3500 dtex is 2 to 350 tex, roughly Ne 295 down to Ne 1.7. A span that wide rarely means one setting covers it all. Expect different tensioners, guides or spindle parts at either end, and compare the configuration being offered, not just the model name. This applies particularly to precision and random winders. A winder such as the XRLT-08 publishes a maximum line speed of 1200 m/min, but that figure alone does not tell you which yarns it covers at that speed.
• 2–140 S/2 is harder to read. If it means two-ply yarn made from singles between Ne 2 and Ne 140, then the delivered yarn runs from about 590 tex down to about 8.4 tex. If the supplier is giving the resultant count instead, the delivered yarn is half that mass, about 295 tex down to about 4.2 tex. Ask which one it is.

The directory summary for the SHRP weft feeder notes that the two yarn-count ranges on its page are not equivalent conversions of each other. Convert both ranges to tex before you compare them with your yarns or with rapier, water-jet and air-jet looms.

Remember the direction as well. Moving to a "higher count" means a finer yarn in Ne or Nm but a coarser yarn in tex, dtex or denier.

Where catalogue shorthand goes wrong

• "S" used loosely. "40S" normally means Ne 40. Some translated catalogues use "S" for any indirect count, Nm included. Ne 40 (14.8 tex) is 1.69 times finer than Nm 40 (25 tex). "S" also stands for twist direction, so a spec line such as "40S/2 S" needs to be read twice.
• "D" for dtex. A supplier who writes "D" but means dtex is off by about 11 %. Watch for familiar sizes such as 167.
• Plied counts stated as singles. Confirm whether "max 60s" applies to the yarn fed in or the yarn taken off. A short-staple two-for-one twister such as the LL321G is described for cotton, flax, wool and blended yarn, so its count limits may be written in more than one system.

What to put in your enquiry

The checklist below suits spinning, twisting and winding machinery. For looms, see what to include in a weaving machinery enquiry.

1. Give each yarn in its own system and in tex or dtex, for example "Ne 40/2 (2 × 14.8 tex, nominal R 29.5 tex)".
2. Say whether every count refers to input or delivered yarn.
3. For filament, give total count and filament number, for example "167 dtex f48".
4. Give fibre type, since the same count runs differently in cotton, polyester or wool. Also give the supply and take-up package.
5. Ask the supplier to confirm the range in writing in tex, and to list any parts that must be changed to cover it.
6. Ask for a trial with your own yarn at the finest and coarsest counts you plan to run. Check the supplier's factory profile before relying on its published range.

Sources

1. ISO 1144:2016, *Textiles — Universal system for designating linear density (Tex System)*, International Organization for Standardization, catalogue page. (accessed 2026-11-04) View source
2. ISO 1144:1973 (first edition, withdrawn), sample pages including Appendix Y conversion tables, ISO via iTeh Standards preview. (accessed 2026-11-04) View source
3. ISO 858:1973, *Fishing nets — Designation of netting yarns in the Tex System*, ISO via iTeh Standards preview. (accessed 2026-11-04) View source
4. ISO 1139:2025, *Textiles — Designation of yarns*, International Organization for Standardization, catalogue page. (accessed 2026-11-04) View source
5. ASTM D2260-24, *Standard Tables of Conversion Factors and Equivalent Yarn Numbers Measured in Various Numbering Systems*, ASTM International, catalogue page. (accessed 2026-11-04) View source
6. "Yarn numbering systems", Swicofil AG yarn manual. (accessed 2026-11-04) View source