Rugs are sold on size, colour and story. They should be sold on knot density, because that single number predicts how the pattern holds, how the pile wears, and how long the thing lasts. Lahore is one of the largest weaving centres in Pakistan, and the range on offer here runs from about 100 knots per square inch to over 600.
What KPSI actually measures
Knots per square inch — count the knots along one inch horizontally, count them vertically, multiply. Higher density means finer detail is possible, because each knot is one pixel of the pattern. A curve rendered at 100 KPSI is visibly stepped; the same curve at 300 is smooth.
- 100–150 KPSI — commercial. Bold geometric patterns only
- 200–300 KPSI — good. Detail holds, wears well under furniture
- 300–450 KPSI — fine. Curves and florals render properly
- 450+ KPSI — very fine, and priced accordingly
How to check it yourself, in the shop
Turn the corner of the rug over. The back shows the knots directly. Put a finger and thumb an inch apart and count — you do not need to be exact, you need to know whether you are looking at ten knots to the inch or twenty. Ten by ten is 100; eighteen by eighteen is over 300. A seller who is happy for you to do this is usually a seller worth buying from.
Density is not the only thing
Hand-spun wool beats machine-spun for how it takes dye — the slight irregularity is what gives an old rug its depth of colour. Vegetable dyes age; chemical dyes fade. And a high-density rug on a cotton foundation will outlast a low-density one on jute by decades.
Ask for the knot count. If it is not offered freely, that is the answer.
