Yarn Count Conversion: Ne, Nm, Tex and Denier Formulas and Tables

Yarn count conversion formulas: Ne, Nm, tex and denier

Count systems fall into two groups. Ne and Nm are length-based (indirect) systems: they give the length of yarn per unit of weight. Tex and denier are weight-based (direct) systems: they give the weight of yarn per unit of length. Because the two groups are inverses of each other, you multiply when converting within a group and divide when converting between groups (TRI 1014).

Source: Cotton Incorporated, TRI 1014, Table 2 (2003). If you work in decitex (dtex), dtex = 10 × tex.

The factors are rounded. With 1 hank = 840 yards (about 768 m) and 1 lb = 453.6 g, the exact factors are tex = 590.54 ÷ Ne and Nm = 1.6934 × Ne; the ISP 1006 bulletin gives the same relationship as “Nm ÷ 1.69336 = Ne”. The results in this article were calculated with the exact factor and rounded to one decimal, so if you use 590.5 and 1.693 you may see small differences in the last digit. In multi-step calculations, round only at the end.

Common Ne values and their equivalents

The same logic works in reverse: Nm 40 is about Ne 23.6, Nm 50 about Ne 29.5 and Nm 60 about Ne 35.4 (Ne = 0.5905 × Nm). A yarn of 150 denier is 16.7 tex, which corresponds to about Nm 60 and Ne 35.4.

How to calculate yarn count from a measurement

A count comes from weighing a known length of yarn. For the four systems, the calculation from a measurement is (MEB, 2014; Çukurova University lab sheet):

• Nm = length (m) ÷ weight (g)
• Ne = length (hanks) ÷ weight (lb); 1 hank = 840 yards ≈ 768 m, 1 lb = 453.6 g
• Tex = weight (g) ÷ length (m) × 1,000
• Denier = weight (g) ÷ length (m) × 9,000

Example 1: metric measurement. You wind a 100 m skein on a reel and weigh it: 2.00 g.

1. Nm = 100 ÷ 2 = 50
2. Tex = 1,000 ÷ 50 = 20
3. Ne = 0.5905 × 50 ≈ 29.5
4. Denier = 9 × 20 = 180

Example 2: a 120-yard skein. For the English count the skein length is usually 120 yards. That is one seventh of a hank (840 ÷ 120 = 7), so Ne = 453.6 ÷ (7 × skein weight in g) = 64.8 ÷ skein weight (g). A 120-yard skein of Ne 30 yarn therefore weighs about 2.16 g (64.8 ÷ 30). TRI 1014 gives the same method in grains: Ne = 1,000 ÷ skein weight (grains).

Example 3: how many metres of yarn are in a kilogram? For Ne 30/1 yarn, Nm = 30 × 1.693 ≈ 50.8, so 1 g of yarn is about 50.8 m long and 1 kg is about 50,800 m (50.8 km). Ne logic gives the same answer: 30 hanks × 840 yards = 25,200 yards per lb, or about 50,800 m per kg. This is the basis for turning a price per kilogram into a cost per metre of yarn. A finer count gives more metres per kilogram: Ne 40/1 (Nm 67.7) is about 67,700 m per kg. So two yarns quoted at the same price per kilogram are not the same price per metre. To compare them, divide: for Ne 30/1, cost per 1,000 m = price per kg ÷ 50.8.

Plied yarn counts: what 30/2 and 20/2 mean

In the cotton (Ne) system the common notation puts the count of a single ply to the left of the slash and the number of plies to the right. A single yarn is written “30/1”; a yarn made by twisting two finer yarns together is written “30/2”. The ISP 1006 bulletin gives this example: two Ne 40 yarns plied together are written 40/2 and are equivalent to Ne 20/1. TRI 1014 adds a warning: in some systems the number written is that of one ply, in others the number of the whole plied yarn. State in the specification which one you mean.

To work out the equivalent count, look at which group the system belongs to (Çukurova University lab sheet; TRI 1014):

• In tex and denier, the counts of the plies are added: 20 tex × 2 = 40 tex; 100 denier/3 is about 300 denier.
• In Ne and Nm, the reciprocals are added: 1/N = 1/N₁ + 1/N₂ + … If all plies are the same, N = single-ply count ÷ number of plies.

Twist changes the equivalent count somewhat (TRI 1014); the values below are approximations that ignore this effect. For an exact value, measure the plied yarn.

If the plies come from different systems, convert them all to one system first. The example from the Çukurova University sheet: an Nm 30 yarn is plied with an Ne 20 yarn. Ne 20 is 20 × 1.693 ≈ Nm 33.9; since 1/30 + 1/33.9 ≈ 0.0628, the plied yarn is about Nm 16.

Plying changes more than the count; it changes how the yarn behaves. According to ISP 1006, plying can increase strength, balance the liveliness (torque) caused by twist, and give a more regular yarn of more even diameter. TRI 1014 adds that it makes yarns more flexible and durable but raises cost. So Ne 30/2 and Ne 15/1 are about the same thickness but are not the same yarn.

Yarn count mistakes in supplier orders

The arithmetic is usually easy; trouble starts when nobody is sure what the number means. Six common mistakes:

1. Leaving out the system. Ne 30 yarn is 19.7 tex; Nm 30 yarn is 33.3 tex, about 1.7 times heavier per metre, which makes it coarser. A quotation that only says “30/1” can be read the wrong way. Always write “Ne 30/1” or “Nm 30/1”, and ask your supplier to confirm the system in writing.
2. Treating Ne as one system for all fibres. The hank length differs by fibre: 840 yards for cotton, 560 yards for worsted wool and 300 yards for linen (MEB, 2014). The same yarn takes a count 1.5 times the cotton count on the worsted system (TRI 1014), so a worsted 30 is as thick as a cotton Ne 20.
3. Treating an “approximate equivalent” as identical. Nm 50 yarn is 20 tex and Ne 30 yarn is 19.7 tex. The gap is about 1.6%: small, but if a supplier swaps one count for the other, that is a substitution and should be recorded in the specification.
4. Confusing the stated count with the measured count. Dönmez (2008), a Turkish master’s thesis, measured ten samples of combed cotton yarn nominally Ne 30 and found values from Ne 28.37 to Ne 28.84 (mean Ne 28.57; measured to TS 244, the Turkish standard). This is a single study and should not be generalised, but it shows that the stated and measured count can differ. A yarn of Ne 28.57 is 20.7 tex, about 5% heavier per metre than Ne 30. Tolerance and test method should be written into the contract.
5. Hiding the rounding. Teaching material routinely rounds converted counts: the Çukurova University lab sheet asks for counts to be expressed as whole numbers, and the MEB module rounds Nm 40, which is really Ne 23.6, to “about Ne 24”. The gap of about 1.6% looks small, but mark any converted value in the specification as “approximate”.
6. Confusing total denier with filament denier. Using the TRI 1014 example: a 450-denier yarn made of 1.5-denier filaments contains 450 ÷ 1.5 = 300 filaments. “Denier” on its own does not say which of the two you mean.

Which count system for which yarn?

The sources divide the systems by yarn group as follows:

ISO 1144:2016 states that the tex system can be applied to all fibres, intermediate products and yarns, and that it contains tables for converting from other systems to tex. The table above is the sources’ general classification; your supplier may quote in a different system, so every quotation line should name the system. To understand what kind of cotton yarn you are buying and how it was spun, see combed, carded and open-end yarn.

Turkish yarn terms on a quotation

Quotations from Turkish suppliers often use local terms. This table maps the ones relevant to this article to their English equivalents.

“Penye” is a yarn process, not a fabric structure, even though it is often used as if it were a fabric name; our T-shirt fabric types guide explains it in more detail.

How yarn count shows up in the fabric

Count affects fabric weight, appearance and the machine it can be knitted on, but it is not the only factor.

• Diameter. According to TRI 1014, assuming the same fibre and the same fibre distribution, yarn diameter is inversely proportional to the square root of the count. Going from Ne 20 to Ne 40 halves the yarn’s weight per length (29.5 tex to 14.8 tex), but its diameter falls by only about 29% (1 ÷ √2 ≈ 0.71).
• Machine gauge. In circular knitting, machine gauge (E) is the number of needles per inch on the cylinder. As E rises, the needles get finer and the yarn used has to be finer too (Dönmez, 2008, p. 12).
• Fabric weight. Models proposed for single jersey weight (Postle, Kurbak) combine yarn count (tex), loop yarn length and loop dimensions (Dönmez, 2008). Dönmez cites Can (2006), who reports that under the same relaxation conditions fabric weight falls as the amount of yarn fed per revolution rises. So the same Ne 30/1 yarn gives different fabric weights at different loop lengths.

Which weight suits which product is the subject of fabric weight by product. For an example of yarn count in a fabric specification, see T-shirt fabric types.

How to check the count of delivered yarn

Yarn count is measured by the skein method. ISO 2060 defines the determination of linear density of yarn from packages by the skein method, except for yarns that have their own standard; the MEB module also refers to ISO 2060 for count determination. The Çukurova University lab sheet bases its steps on the Turkish standard TS 244:

1. Take samples. Select a number of packages at random from the lot or from the machines, enough to represent the lot; the sheet leaves the number of samples to TS 244. The MEB module gives one skein from each of 10 packages as an example.
2. Condition them. Keep the samples in a standard atmosphere (20 ± 2 °C, 65 ± 2% relative humidity) for at least 6 hours; for samples already in skein form this can be as little as 1 hour. Conditioning is complete when two weighings made 2 hours apart differ by less than 0.25%.
3. Wind skeins. For tex, denier and Nm, prepare skeins of 100 m; for Ne, skeins of 120 yards. Take at least two test specimens from each package.
4. Weigh. The balance should be accurate to at least 0.2%. Take more than one measurement and calculate the mean and the coefficient of variation. Electronic or mechanical count balances can also give the result directly (MEB, 2014).
5. Calculate and convert. Calculate the count with the formulas above and, if needed, convert it to the system named in the contract.

For yarn taken from a woven fabric, the same sheet gives a separate method based on TS 255: cut strips wide enough to give at least 50 yarns; take the first ten yarns, straighten their crimp by hand tension and measure their corrected lengths; then weigh all 50 yarns together and calculate tex as weight ÷ length × 1,000. For yarn taken from a knitted fabric, this article gives no sourced method.

If you need a measurement that will stand as the basis of a contract, have it done by a test laboratory. You can find firms in the test laboratories category of our company directory.

How to write yarn count in a specification

The list below is a starting point for writing yarn count so that it cannot be misread:

1. System, count and ply: Ne 30/1, Ne 20/2, Nm 60/1, 150 denier.
2. Fibre and composition: 100% cotton or cotton-polyester, with percentages.
3. Yarn type: combed or carded; ring-spun or open-end. How these differ is explained in combed, carded and open-end yarn.
4. Governing count: if a converted value is for information only, say so. Example: “Ne 30/1 (governing), Nm 50.8 (approximate, for information).”
5. Test method and tolerance: which standard is used (for example the ISO 2060 skein method), the conditioning atmosphere, and the permitted deviation from the count. Buyer and supplier agree the deviation limit together.
6. For filament yarns: write total denier and filament count separately.

An example specification line: “100% cotton, combed ring-spun yarn, single ply Ne 30/1 (governing count); count determined by the ISO 2060 skein method in standard atmosphere.” The price question comes once the count is settled; how yarn prices form is covered in what drives yarn prices.

Summary

Yarn count is a relationship between length and weight. Four factors are enough for conversion: tex = 590.5 ÷ Ne, Nm = 1.693 × Ne, denier = 9 × tex, dtex = 10 × tex. For plied yarns, add the counts in tex and denier and add the reciprocals in Ne and Nm. Write the system name next to every count, mark converted values as “approximate”, and put the tolerance and test method into the contract. If you are looking for a yarn supplier, browse the cotton yarn, blended yarn and polyester yarn companies in our directory.