The thread numbering

The thread numbering

- Categories : Maison Sajou

Thread Numbering: A Complex Science

Differences between manufacturers and evolution of methods

Thread numbering is a complex subject. Often, each manufacturer has their own habits, and a number from one company may not correspond to the same number from another.
Even if there are basic principles, these have evolved over time, and not all manufacturers have necessarily followed these changes, maintaining older practices.

Influence of French and British traditions

Alongside France, Great Britain has been one of the major suppliers of thread, and as everyone knows, the British, although officially adopting the metric system since the 1970s, don’t count quite like the others...
In addition, the method of calculating thread count varies depending on the type of material involved.

Thread numbering by material type

Cotton: metric numbering (NM)

In France, since 1942, numbering for cotton uses metric numbering (NM): a thread measuring 1,000 metres with a constant weight of 1,000 grams. Thus, a no. 1 thread weighs 1,000 grams for 1,000 metres, and, for example, a no. 40 thread weighs 1,000 grams for 40,000 metres.

Before 1942, French numbering was used, where 1,000 metres of thread would weigh 500 grams.

For English cotton yarn count (NE), the base is 840 yards (768.1 metres) weighing one English pound (453.6 grams). To convert English numbering (NE) to metric numbering (NM), divide the English number by 0.5905.

Combed wool: regional practices and metric numbering

For combed wool, metric numbering is the standard, but regional practices persist. In Alsace, calculations were based on 700 metres for 500 grams, while in northern France, they used 720 metres for 500 grams.

Linen yarn: English numbering and skein tradition

The numbering of linen yarn is based on English numbering. A no. 1 linen thread is a skein of 300 yards (274 metres) weighing 453 grams (1 English pound). Traditionally, linen was sold in bundles of 100 skeins, with each skein composed of 12 hanks.

For example, a bundle of 100 skeins no. 1 contains 360,000 yards or 329,184 metres and weighs 543.6 kilos. However, in France, the standard weight adopted is 540 kilos. For the calculation: a no. 36 in English numbering is 36 x 10/6 = 60, and conversely, a no. 40 in French numbering is 40 x 6/10 = 24.

Silk threads: denier count and metric numbering

For silk threads, the calculation is different: the unit of length is 450 metres, and the count is expressed in demi-decigrams (5 centigrams), also called denier. Alternatively, it is possible to define the number of grams in 9,000 metres of thread. For example, if a silk thread measuring 450 metres weighs 1,500 grams, the count (TD) is calculated as 1,500/0.050 = 30 deniers. If a hank of 9,000 metres weighs 150 grams, its count will be 150 deniers. To convert between metric numbering (NM) and denier count (TD), the calculation is: NM ÷ (9,000/TD), and for the inverse, 9,000 ÷ NM. For example, an NM 60 will correspond to 9,000 divided by 60, or 150 deniers.

Nylon and rayon threads: specific calculation methods

For nylon threads, the calculation follows the same method as for silk, whereas for rayon, the metric numbering system (NM) is used.

Conclusion: an exact science with many variables

In summary, although thread numbering is an exact science, calculation methods vary between manufacturers due to historical, traditional, and regional factors.

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