Cotton sewing thread - Fil Au Chinois

How is the sewing thread thickness calculated? We are asked this question on an almost daily basis. It is not simple, especially as the calculation differs in function of the sewing thread. In principle, France uses metric numbering (NM) since 1942 for cotton yarn: a thread measuring 1,000 metres with a constant weight of 1,000 grams. Thus a N°1 is a thread which weighs 1000 grams for 1,000 metres and, for example, a N°40 is a thread weighing 1,000 grams for 40,000 metres. But, for historical reasons, not all the producers follow this rule. You will find a detailed article about sewing threads numbering Madame Sajou's Diary.