Quality/Knots Per Square Foot

KPSF is an abbreviation for "Knots Per Square Foot" . KPSF is one measure of a hand knotted carpet's quality. The higher the knots per square feet, the higher the carpet's quality on this measure. Other determining factors of quality include the intricacy of design, the type of wool/silk used, uniqueness of design, clarity of the face of the rug, and so on.
Typically, higher knot counts are found in rugs with floral or curvilinear patterns. The higher knot count allows the curves to be formed more elegantly and enables flowers and leaves to be more intricately woven. Geometric-patterned rugs usually have lower knot counts than floral patterns, as the geometric shapes tend to have straight lines and angles, which do not require as many knots per square inch. The type of pattern and appearance desired of a rug often dictates the number of knots per square inch required.
A higher knot count rug is often more expensive than a lower knot count rug of the same design and origin, everything else being equal, as the weave is finer and more time has been spent on the rug. On the other hand, a rug of different design and origin may be more expensive, even though it has a lower knot count.
Keep in mind that knot count is only one measure of a rug's quality. Also, a word of caution on judging rugs on knots per square inch: some dealers tend to inflate the figure.

Article From Bosi Carpet, www.bosi-carpet.com