There are three systems of yarn count are currently in use: the fixed weight, the fixed length and the Tex systems.

Originally, when the yarn count is not known, it can be established by measuring a length of 10, 50, or 100 metres, depending on the count you judge the yarn to be. This is best done on a swift ( a skein winder) set to a circumference of 1 meter. The hank is then weighed in grams. Eg, if 50 meters of yarn weighs 2 grams, 1000 meters will weigh 40 grams and the count is therefore 40 Tex. The unit length of 1s count (i.e.: 1 unit count of 1 lb weight) varies with different fibres and spinning systems.

The fixed length system and the Tex system are based on metric weights and measures. Tex is an internationally agreed system of yarn numbering that applies to all types of yarns, regardless of the method of production.

The fixed weight yarn count system is used for numbering spun yarns. It can be used with British and American weights and systems. It is based on the length of the yarn per kg weight. The greater the length of the yarn weighing 1 kg, the finer it is, and the higher the count number. The count number gives the number of unit lengths, I.E.: skeins, hanks, etc, in 1 lb.;. E.g.: 10 hanks of cotton is abbreviated to 10s cotton. 12 skeins Yorkshire woolen spun is abbreviated to 12s Y.sk. and the direction of the twist is included in the formation.

The Tex system is also based on the fixed length system. Ie: Weight per unit length. The Tex count represents the weight in grams per 1 kilometer (1000 meters) of yarn. For example, a yarn numbered 10 Tex weighs 10 grams per kilometer. The Tex number increases with the size of the yarn.