Knot density
The knot density is the number of knots per square metre. It is obtained by counting the knots on the backside of the carpet - 10 cm in the direction of the warp and 10 cm in the direction of the weft. Multiply the number of knots in each direction with each other and then multiply the result with 100. The number given is the number of knots per square metre.
Arithmetical problem:
(40x50 = 2 000 knots per square metre, 2 000x100 = 200 000 knots per square metre).
The symmetrical knot gives two "pinheads" in the direction of the warp, which must be observed for when calculating.
If you open up the carpet on the right side and look down with a magnifying glass it is possible to see which knot has been used.
Knot density is not the most important factor with regard to the quality of hand-knotted carpets, despite what many people think. What is actually more important here is the quality of the yarn used in the manufacture of the carpet. If a thicker yarn is used, there will be fewer knots in the carpet and a finer yarn will produce more knots. The yarn used is determined by the person knotting the carpet. This also means that the same type of carpets may have a larger volume in terms of the number of knots in them.
The finer the wool used, the better the quality of the carpet as the knot density is actually not the most important factor for determining the quality of a hand-knotted carpet. For example, a Persian Gabbeh, which does not have a particularly high knot density, is a high-quality carpet because of the fine wool used. A carpet that feels tight does not necessarily have a lot of knots, but this comes about due to how tightly compressed the knots are in the carpet.