Knots Per Square Inch

Count the knots but knots don’t count.

Tribal Afghan Rug

Knot per square Inch is the knot density in a square inch of space. that a literal meaning. But do you know the quality of a rug does not only indicated by counts of KPSI, there are other factors which must need to be considered like origin, tribe or village where the rug came from. Each origin has its own traditional count specific to its area. For example, a medium count of 200 might be the finest quality produced by some tribe. In turn, the high knot count of 1000 might not be the finest quality in some region, where finest rug from the area might be of 3000 knots count normally. Therefore purely counting knots without considering the origin and type of the rug is fairly not a good indication of quality and value.


Counting knots correctly.

Counting knots on an oriental rug is easy to learn. Unfortunately most “expert” knot counters do not realize two knots is often counted as one knot . We must first learn what one knot looks like from the rug’s back. On the back of a handknotted rug you will see thousands of tiny squarish “bumps” (see below). These squarish “bumps” are the visible parts of the knots that loop around the warp threads as shown below.knots per square inchpersian knots

Every Persian and Turkish knot has two loops but only some rugs show both. Most rugs show only one of the loops.

Before counting knots we must be sure we are counting each knot only once.


Grading System and Nomenclature.

China, India and Pakistan each use their own unique system for grading rug quality by knot count. Handmade rugs from any country (except China) are often graded by Knots Per Square Inch, or KPSI – an important measure of a hand knotted rug’s quality, value and even durability. A rug with a higher knot count will typically possess the attributes of greater intricacy and clarity of design, and is usually more expensive than a rug with a lower knot count, but with similar design features etc. It can easily be understood as more pixel make the picture clear same as more knots make the design more clear and intricate.

  Knots Per Square Inch (KPSI)     RUG QUALITY RATING
  KPSI Corresponds to the Pile Density of Wool
30 KPSI Very Coarse
30 – 60 KPSI Coarse
60 – 130 KPSI Medium Fine
130 – 160 KPSI Fine
160 – 290 KPSI Very Fine
290 + KPSI Extremely Fine

By now you should be ready to apply these systems on real rugs! They are not so difficult to learn (a magnifying glass and a ruler may be helpful), but remember – Indian and Persian design rugs show each knot only once, but a Pakistan rug shows each knot twice.


India developed a quality rating system that we have listed below. Two numbers are used as such; 9/9. The first number is the number of knots in 9/10 of an inch of the rugs width. The second figure is the number of knots in 4 1/2 inches of the rugs length. This is the conversion chart to knots per square inch (KPSI)

Quality   KPSI (knots per square inch)

3.5/32      28
5/28         35
5/32         40
6/6           36
6/40         59
6/45         67
7/18         31
7/40         69
8/8           64
8/36         71
9/9           81
9/25         56
9/54         120
9/60         133
10/10       100
10/14       140
10/32       79
10.5/48    124
11/32       87
12/60       178
13/65       209
14/14       196
16/80       316


All Chinese rugs are graded by “line count”. Common line counts include “70 line”, “80 line” and “90 line” etc.

A ruler of 12 inches is used to count the number of pairs of warps in one linear foot. Since the construction is square, you multiply the number of pairs of warps or the “line” count by itself and divide by 144 for the number of knots per square inch. For example 120 line is 120 x120 then divided by 144 or 100 knots per inch.

Iran: (Persian)

Persian rugs are based on a unit of measure called “raj” or about 7 cm. Most, but not all, of the best rugs have a square knot construction or the same number of knots in both width and length. Below is a basic chart converting raj to knots per square inch.

Raj     KPSI

30      118

40      210

50      329

60      473

70      675

90      1066

Pakistanpakistan knots per square inch

Pakistan Bokhara rugs such as 8/14, 9/16 or 10/20 quality show each knot twice (as shown here). Notice the first number is roughly one half the second, because on this type of rug only half as many knots can fit in the width. On ‘Persian quality’ (Persian design) Pakistan rugs such as 13/15, 16/18 & 20/20 each knot shows only once (see above). Notice both numbers are equal or near equal because more knots can fit into the width.


Acknowledgement and Sources:

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