Yarn count is the number that tells you how coarse or fine a yarn is. Mills and laboratories use several systems: tex and decitex, denier, metric count (Nm) and English cotton count (Ne). This article explains what those systems mean, how to convert between them with published factors, how plied yarns are described, and how linear density is measured by the skein method.
Yarn count is not fabric weight: fabric mass per unit area is GSM, grams per square metre, and you cannot read GSM from count alone. It is also not knitting-machine gauge. How a count is chosen for a needle bed is covered in Knitting Machine Gauge Explained.
Direct and indirect systems
All common numbering systems relate a mass to a length. They fall into two families.
Direct systems express linear density: the mass of a stated length. Tex, decitex (dtex) and denier belong here. In a direct system a larger number means a coarser, heavier yarn. Coats, in its Thread Numbering bulletin, groups these as fixed-length systems, because a unit length is taken as fixed and the mass of that length is measured.
Indirect systems express a count: the length of a stated mass. Metric count (Nm) and English cotton count (Ne) belong here. In an indirect system a larger number means a finer yarn. Coats groups these as fixed-weight systems, because a unit mass is taken as fixed and the length of that mass is measured.
The words “fixed length” and “fixed weight” are not used consistently everywhere in the trade. AMANN describes the same two families and the same finer/coarser rules, yet it applies those labels the other way round. When a document says only “fixed-length system”, read the definition, not just the heading. The reliable distinction is direct (mass per unit length) versus indirect (length per unit mass).
What the main systems mean
The international reference for the Tex System is ISO 1144:2016. The official scope, as given in the EVS catalogue, is that the standard gives the principles and recommended units of the Tex System, includes conversion tables for calculating the tex values of numbers or counts in other systems, and states a procedure for implementing the system in trade and industry. It applies to all kinds of textile fibres, intermediate products (for example tops, slivers and rovings), yarns and similar structures. EVS records the second edition as valid from 14 September 2016.
The unit definitions below are those published by Coats and, where the wording helps, by AMANN. They agree with each other and with the SI equivalents tabulated by NIST.
Tex is the mass in grams of 1,000 metres of yarn. AMANN’s example is that 10 tex means 1,000 metres of the sample weigh 10 grams. The NIST Guide to the SI, Appendix B.8 lists the exact conversion 1 tex = 1.0 × 10⁻⁶ kilogram per metre, which is the same relationship.
Decitex (dtex) is the mass in grams of 10,000 metres, so dtex is ten times tex for the same yarn: 20 tex is 200 dtex. Filament yarns are often written in dtex.
Denier is the mass in grams of 9,000 metres. NIST tabulates 1 denier = 1.111 111 × 10⁻⁷ kilogram per metre, which is one-ninth of the tex factor, so denier = 9 × tex. Denier remains familiar for filament yarns and for some consumer products.
Metric count (Nm) is the number of hanks of 1,000 metres in one kilogram, which is the same as the length in metres of one gram. AMANN’s example is that Nm 10 means 1 gram of the sample is 10 metres long. A higher Nm is a finer yarn.
English cotton count (Ne), also written Nec or Ne B, is the number of hanks of 840 yards in one pound. Coats’ example is that Ne 1 means one pound contains 840 yards, and Ne 5 means it contains 4,200 yards (840 × 5). A higher Ne is a finer yarn.
ISO 2947:1973 is a changeover document rather than a set of exact factors: its official scope is to facilitate the move from traditional numbering systems to tex by providing recommended rounded tex values to replace yarn numbers in the six main traditional systems. ASTM D2260-24 is the current ASTM collection of conversion factors and equivalent yarn numbers; its official scope states that its content is basically consistent with ISO 2947. Use the edition named in a specification. The worked table later in this article is calculated from freely published Coats factors, not copied from those paid standards. This article does not quote hank lengths for worsted, woollen or linen lea counts, because the cited public pages do not state them.
Converting between systems
Coats publishes the following conversion relationships. They are the factors used for every worked number in this article.
- tex = 1,000 / Nm
- tex = 590.54 / Ne
- tex = denier / 9
- tex = dtex / 10
- dtex = 10 × tex
- denier = 9 × tex
- Nm = 1,000 / tex
- Ne = 590.54 / tex
- Nm = Ne × 1.6934
- Ne = Nm × 0.5905
AMANN publishes the same relationships with more heavily rounded constants (590 and 0.59). For a specification or a laboratory conversion, prefer the more precise Coats factors, or the official tables in ISO 1144 or ASTM D2260 when those documents are named in the order.
The constant 590.54 follows from the definition of cotton count together with official SI factors. Coats defines Ne as the number of 840 yard hanks per pound. NIST lists 1 yard = 9.144 × 10⁻¹ metre (0.9144 m; factors in boldface in Appendix B.8 are exact) and 1 pound (avoirdupois) = 4.535 924 × 10⁻¹ kilogram (0.4535924 kg). Then, as arithmetic:
840 × 0.9144 = 768.096 metres
0.4535924 × 1,000 = 453.5924 grams
tex of Ne 1 = 453.5924 / 768.096 × 1,000 = 590.541, which rounds to the Coats factor 590.54.
Worked conversions (arithmetic)
These examples use the Coats factors, rounded as stated. They are not measured yarns.
Example 1. Convert 30 tex to cotton count. Ne = 590.54 / 30 = 19.6846..., which is 19.68 Ne at two decimal places.
Example 2. Convert 40 Nm to tex. tex = 1,000 / 40 = 25 tex exactly.
Example 3. Convert 150 denier to tex. tex = 150 / 9 = 16.666..., which is 16.67 tex at two decimal places. The same yarn is 166.7 dtex (10 × 16.67).
Example 4. Convert 20 Ne to metric count. Going through tex keeps the rounding consistent: tex = 590.54 / 20 = 29.527 tex, then Nm = 1,000 / 29.527 = 33.867..., which is 33.87 Nm at two decimal places. Coats’ direct factor Nm = Ne × 1.6934 gives 20 × 1.6934 = 33.868, which rounds to the same two-decimal figure.
The table in the diagram is calculated from the same factors, starting from the tex column: Nm = 1,000 / tex, Ne = 590.54 / tex, dtex = 10 × tex and denier = 9 × tex, with Nm and Ne rounded to two decimal places where the value is not a whole number. The rows are rounded conversions, not a list of commercial products.
Ply notation and resultant count
A folded or plied yarn is made from more than one single. The number that matters for most specifications is the resultant count of the finished thread. Coats gives two rules:
- In fixed-weight (indirect) systems: resultant size = individual yarn count / number of plies.
- In fixed-length (direct) systems: resultant size = individual yarn count × number of plies.
A particular resultant size can be made with any number of plies.
Example 5 (arithmetic). Two plies, each of Nm 30 singles, have a resultant metric count of 30 / 2 = 15 Nm.
Example 6 (arithmetic). Two plies, each of 20 tex singles, have a resultant linear density of 20 × 2 = 40 tex. The same yarn is 400 dtex.
Those calculations assume that folding does not add or remove mass other than the second ply. Twist, a binder or finish can move a measured result slightly; the measured resultant, by a named method, is then the number to report.
Written shorthand such as 2/30 Nm, 30/2 Nm or 30/1 Ne is common, but it is not a single universal code. In some cotton-spinning documents the first number is the singles count and the figure after the stroke is the number of plies (30/1 for a singles 30 Ne yarn; 30/2 for two plies of 30 Ne, resultant 15 Ne). In some metric knitting documents the number of plies is written first (2/30 Nm for two plies of Nm 30, resultant 15 Nm). The two forms can be read as opposites if the convention is not stated. Write the singles count, the number of plies and the system in words, then give the resultant by the Coats rule.
ISO 1139:2025, also published as BS ISO 1139:2025 on 31 December 2025, specifies two methods of indicating the composition of single, folded, cabled or multiple-wound yarns. The official notation comprises linear density in the Tex System, the number of filaments in filament yarns, the direction and amount of twist, and the number of folds. It is not applicable to some special yarns, including fancy, textured or bulked yarns and yarns produced by wrapping a material round a core. Where a specification calls for ISO 1139, follow that standard rather than an informal stroke notation.
Sewing-thread ticket numbers are a further commercial shorthand. Coats notes that a ticket number is the manufacturer’s reference for the size of a given thread, that a higher ticket number is a finer thread, and that a Ticket 40 in one thread type is not the same as a Ticket 40 in another.
Count, diameter and fabric weight
Linear density is not yarn diameter. Two yarns can share a tex value and still differ in diameter if the fibre density, the twist or the bulk is different. This article does not give a diameter formula, because none of the cited public pages states one.
Nor is yarn count a fabric GSM. GSM is mass per unit area of the cloth, measured on a known area by a named method, as explained in the fabric GSM article. To go from yarn linear density to fabric mass you also need the construction, and after dyeing and finishing you need a measurement. Garment merchandisers who put a count on an order should name the system, the resultant of any ply, and, where fabric weight is also specified, a GSM method and fabric state.
Measuring count: the skein method
Count on a package label is a nominal figure. When the number must be checked, the usual laboratory method is to reel a known length into a skein, weigh it, and express the result in the required numbering system. ASTM D1907 notes that the same skeins may also be used later for skein breaking strength.
Two current methods cover this work. They are related, but they are not interchangeable on every yarn.
ISO 2060:1994 specifies a method for the linear density of all types of yarn in package form. The official abstract states that it includes seven optional procedures based on different methods of conditioning and preparation; that it applies to single, folded and cabled yarns; that it is not applicable to yarns which stretch more than 0.5 per cent when the tension, in centinewtons per tex, increases from 0.5 to 1.0; and that it is not applicable above 2,000 tex. EVS records the standard as valid from 17 November 1994.
ASTM D1907/D1907M-12(2025) is the current ASTM skein method (the store lists the 12R25 edition as active). Its official scope covers yarn in package form, with provision for expressing the result in all the traditional numbering systems. It applies to yarns that stretch less than 5 per cent when tension increases from 0.25 cN/tex to 0.75 cN/tex; by agreement, and with a lower reeling tension, it may be adapted to yarns that stretch more than 5 per cent. It applies to yarns finer than 2,000 tex, and may be adapted to coarser yarns with shorter skeins and alternate reeling conditions agreed by the parties.
The stretch limits are not the same (0.5 per cent under one tension pair in ISO 2060; 5 per cent under a different pair in ASTM D1907). A result from one method should not be treated as a result from the other without agreement.
ASTM D1907 sets out seven options, depending on whether the yarn is scoured, whether it is weighed conditioned or oven-dry, and whether commercial moisture regain or a commercial allowance is added. Option 1 (unscoured, conditioned yarn) is generally used for yarns spun on the cotton system. Options 6 and 7 (scoured, oven-dried yarn, plus commercial moisture regain or allowance) are generally used for filament yarns, or yarns containing wool fibres. The parties must agree the option, or follow the one prescribed in the relevant method or tolerance. ISO 2060 likewise has seven optional procedures, based on different methods of conditioning and preparation.
Moisture and finish change the mass of a skein, just as they change a fabric GSM. Always report the method, the option or procedure, and the state of the yarn. For laboratory fabric tests more generally, see Fabric Testing: Methods, Equipment and What Results Mean.
FAQ
What is the difference between tex and Nm? Tex is a direct system: grams per 1,000 metres. Nm is an indirect system: metres per gram, or 1,000 metre hanks per kilogram. They are exact reciprocals: tex = 1,000 / Nm, and a higher tex is coarser while a higher Nm is finer.
How do I convert Ne to tex? Use tex = 590.54 / Ne, the factor published by Coats. For 30 tex that is 19.68 Ne at two decimal places (590.54 / 30, arithmetic). For an official table, use ISO 1144 or ASTM D2260 as named in the specification.
Is denier the same as dtex? No. Denier is grams per 9,000 metres; dtex is grams per 10,000 metres. For the same yarn, denier = 0.9 × dtex, or denier = 9 × tex. A 150 denier yarn is 16.67 tex, or 166.7 dtex, at the rounding used above.
What does 2/30 Nm or 30/1 Ne mean? Treat these as trade shorthand, not as a single international code. Confirm whether the first figure is the number of plies or the singles count, then apply the Coats rule: divide in Nm or Ne, multiply in tex or denier. Two plies of Nm 30 singles have a resultant of 15 Nm. If a specification requires a standardised designation, use ISO 1139 in the Tex System.
Can I calculate fabric GSM from yarn count? No. Count is mass per unit length of the yarn. GSM is mass per unit area of the fabric. You need the construction as well, and after finishing you need a measurement against a named fabric method. See the fabric GSM article.
Which method should a laboratory use to measure yarn count? Name the method in the specification. ISO 2060 and ASTM D1907 are both skein methods for yarn in package form, but they have different stretch limits and their conditioning options must be agreed. Report the option, not only the number.
Does a higher count always mean a finer yarn? Only in indirect systems (Nm, Ne). In direct systems (tex, dtex, denier) a higher number is coarser. Always name the system.
Sources
- ISO 1144:2016 (EVS catalogue; official scope: principles and recommended units of the Tex System, conversion tables, implementation procedure; fibres, intermediates, yarns; valid from 14 September 2016).
- ISO 2947:1973 (EVS catalogue; official scope: recommended rounded tex values to replace traditional yarn numbers in the six main systems).
- ASTM D2260-24 (official scope: conversion factors and equivalent yarn numbers; content basically consistent with ISO 2947; current edition).
- ISO 2060:1994 (EVS catalogue; official abstract: skein method, package-form yarns, seven optional procedures, stretch and 2,000 tex limits).
- ASTM D1907/D1907M-12(2025) (official scope and significance: skein method, traditional numbering systems, 5 per cent stretch limit, 2,000 tex, seven options).
- ISO 1139:2025 and BS ISO 1139:2025 (official scope: designation of single, folded, cabled or multiple-wound yarns in the Tex System; published 31 December 2025 as the British adoption).
- Coats, Thread Numbering (Bulletin 05) (definitions, conversion factors including 590.54, resultant-count rules, ticket numbers).
- AMANN, Textile numbering systems (tex, dtex, denier, Nm and Ne B definitions; conversion formulae with rounded constants).
- NIST Guide to the SI, Appendix B.8 (1 tex = 1.0 × 10⁻⁶ kg/m; 1 denier = 1.111 111 × 10⁻⁷ kg/m; 1 yard = 9.144 × 10⁻¹ m, exact where boldface; 1 pound avoirdupois = 4.535 924 × 10⁻¹ kg).
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