Rugs Made by People NOT Machines

Have you ever heard of KPSI, Knots per Square cm or Knots per square meter? Do you know how many knots your rug has?

I thought it’s worth explaining some of these words and what they really mean. This particular post is about the rugs knots density and how it is measured.

What is “knots density”?

Knots density is the number of knots a carpet has for a given metric. You can compare this to the number of pixels you have in your camera. The more pixels you have, the more detailed your picture will be.

Knots density makes sense when your rug has knots (Gordes or Turkish double knots, Persian single knots or other type of knots). You cannot really speak of knots density for rugs that are weaved like Kilim rugs or embroidered like Soumak or Suzani rugs.

Does it really matter? Is it a quality indicator?

Well, Yes and No! Some people say that the higher the density of knots, the better the quality of your rug is. This is not really true: you cannot only use knots density as an indicator of quality. To give you an example, a bad quality Kayseri rug with high knots density can be cheaper than a good quality Dosemealti Nomad carpet with lower knots density. This is like comparing apples with pears. Having said that, within the same category, the same origins and with other quality factors being similar, knots density matters.

Wool Hereke rug with high density

Low knots density Shirvan rug

Depending on the material used in a rug – wool, cotton warp or silk – you would expect various knot density. Silk by nature is thiner than wool – so you should expect higher density of knots in Silk rugs than in Wool rugs.  Here you can see what I would consider as a “high density rug”.

High knots density Silk rugs would start from

• 100 knots per square cm
• or 1,000,000 knots per square meter
• or 645 knots per square inch (KPSI)

High knots density for Wool rugs starts from

• 25 knots per square cm (equivalent to what is below)
• or 250,000 knots per square meter
• or 160 knots per square inch (KPSI)

Are you lost in all these metrics? Let’s see how to estimate a rug knot density.

In order to calculate the “knot density”, you simply have to count the number of knots you have per square metric choosen.

Usually, the knots density is expressed as:

1. Knots per square cm – or Knots per square meter
2. Knots per Square Inch (KPSI) – or Knots per Square Foot.

Let’s go through these metrics.

1. Knots per square cm (or Knots per square meter): You simply “draw” a square of 1 cm by 1 cm on the back of your rug and count the number of knots that fits in this square. For example, if you count 25 knots within this square, then you will have a density of 25 knots per square cm.
   Convert Knots per square cm to Knots per square meter: 25 knots per square cm is equivalent to 25 * 100 * 100 = 250,000 knots per square meter.
2. Knots per Square Inch (KPSI). Similar to the previous point, in this case, you “draw” a square of 1 inch by 1 inch and count the number of knots that fit in.
   Convert KPSI to Knots per square cm: 400 KSPI is equivalent to (400 / 2.54) / 2.54 = 400 / 6.4516 = 62.0 Knots per square cm. Bear in mind that 1 cm is 2.54 times smaller than 1 Inch so you have to divide.
   Convert KPSI to Knots per square Foot: There are 12 inches in 1 foot so 400 KPSI is equivalent to 400 * 12 * 12 = 400 * 144 = 57,600 Knots per Square Foot.

Let’s recap all the conversions:

• Convert knots per square cm to knots per Square meter: multiply by 10,000
• Convert knots per square Inch (KPSI) to knots per square cm: divide by 6.4516.
• Convert knots per square Inch (KPSI) to knots per square Foot: multiply by 144.

Let’s go through an example – How many knots does your 6′ by 9′ rug have?

Let’s say you have a rug that is 6′ by 9′ (6 foot by 9 foot – or 183 cm by 274 cm) with an estimated 400 KPSI (Knots per Square Inch). How many knots your rug has?

• 6′ by 9′ rug means that your rug is 6*9 = 54 square foot.
• Convert the KPSI to Knots per Square foot: 400 * 144 = 57,600 Knots per square foot
• So your rug has a total estimate of 54 * 57,600 = 3,110,400 knots! Yes that’s over 3 million knots.

I hope this post will make it easier to understand KPSI and knots density. Do you know how many knots your rug has in total? Go and count it and let me know