The fiber is the basic component of textile products.
The fiber has a long and thin shape. It can only be loaded by tension.

The yarn is made of many fibers by spinning. Spinning requires a certain minimum length for the fiber of at least 10mm.

The thread is produced by twisting several yarns together.

Weight numbering yarn count and titer

The yarn count or titer is specified as the weight per unit of length. It is also known as "Weight numbering" of yarns.
In the SI system of units the meter is the unit of length, the gram is the unit of weight.
The derived unit "tex" (abbreviation Tt) describes the yarn count of the fiber in gram / kilometer:

1 tex = 1g/1000m
1 dtex (decitex) = 0.1 tex or1 gram per 10.000 meter
1 ktex (kilotex) = 1.000 tex or1 gram per 1 meter
The tex is common with chemical fibres "nylon", "Perlon", PA6, PA6.6 and with filaments.

The denier or "den" is widespread but non-standard, for example, in women's tights. The "den" comes from the French "denier".

The ratio of a den to the weight of the yarn per 9000m is specified:
1 den = 1g/9000m

Therefore the tex can be converted to den:
1 tex = 9 den

Length numbering fineness and run length

The length per unit of weight is specified in case of fineness or run length.
The unit for the fineness is the "numbering" Nm.
The fineness is specified for yarns, especially for wool yarns.
1Nm = 1m/1g (meter per gram)

In addition to the "numbering" in meters and grams, there is also English and French numbering.
NeB: English numbering for cotton
NeL: English numbering for linen
Furthermore, there are:
Nek: English numbering for worsted yarn
NeW: English numbering for carded yarn
Nf: French numbering for cotton

The NeL (Nr. English linen) is defined as 300 yards per pound (lb)
1 NeL = 0,604772 Nm

The NeB (Nr. English cotton) is defined as 840 yards / per pound (lb)
1 NeB = 1,6934 Nm

Conversion of tex to Nm

weight numbering: 1 tex = 1g/1000m
Length numbering: 1 Nm = 1m/1g
1 tex = 1000 / Nm
1 Nm = 1000 / tex