Calculation/Conversion Chart:

Tex:
dtex:
Den:
Nec:
Nm:
Worsted:

No. of grams per 1'000 meters
No. of grams per 10'000 meters
No of grams per 9'000 meters
No. of 840 yards per round
No. of 1'000 meters per 1'000 grams
No. of 560 yards per pound

Note the following procedures for multi-ply yarns:

The Tex system typically names the total count of all single yarns.
Therefore, a yarn with 40 Tex 2 ply is equal to 80 Tex single.

The Denier system typically names the total count of all single yarns.
Therefore, a yarn with 1000 Den 4 ply is equal to 4000 Den single.

The Nm system typically names the count of the single yarn only.
Therefore, a yarn Nm 40/2 is equal to Nm 20/1.

The Nec system typically names the count of the single yarn only.
Therefore, a yarn Nec 40/2 is equal to Nec 20/1.

Clima:

To prevent extreme liveliness of yarn (snarls etc.) and high static charge of the yarn, it is recommended to have a relative humidity of ~50% - 60% and a temperature of 72 - 75 ºF resp. 22 - 24ºC