Rug Weave Density: What Knots Per Square Inch Mean
Weave density tells you how many knots a hand-knotted rug has in a given area. It is one of the main signs of how fine a rug is and how much work went into it.
How density is measured
- KPSI (knots per square inch) is the most common measure.
- Knots per square metre is used in many countries. One square inch is about 6.45 square centimetres.
- Raj is a traditional Persian measure: the number of knots across about 7 cm. You may see a fine Tabriz described as "50 raj", for example.
How to count the knots yourself
- Turn the rug over.
- Use a ruler to mark one inch (2.54 cm) along the width.
- Count the knots across that inch. Each knot looks like a small bump of colour.
- Count the knots along one inch of the length.
- Multiply the two numbers. For example, 12 across x 14 down = 168 KPSI.
What the numbers mean
As a rough guide, coarse village and tribal rugs can have fewer than 100 KPSI. Good city rugs are often a few hundred KPSI. The finest silk rugs, such as some from Qom, can go much higher.
Is higher always better?
No. Higher density allows finer, more detailed designs and usually means more months of work. But a coarser, thick tribal rug such as a Heriz can be tougher in a busy room than a very fine silk rug. Quality also depends on the wool, the dyes and the skill of the weaver. Read how to value a Persian rug.
Machine-made rugs
Machine-made rugs are often described by points per square metre instead of knots. The numbers cannot be compared directly with a hand-knotted rug. See handmade vs machine-made rugs.
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