If you are purchasing a rug online, specifically ask for a photo of the kpsi! On numerous occasions, we have seen sellers counting a double ply knot as two separate knots rather than one single! Although there are many ways to measure your carpet's knot count, in general, KPSI (Knots per Square inch) is the most common standard of measure in the U.S. Scroll to the bottom of this page for instructions on how you may count the knots of your rug. For purposes of the rug estimator pro, all programming has been made with the use of standard U.S. quarters. Quarters are slightly smaller than 1"x1", however we suggest you use this for the most accurate results.
For purposes of the Rug Estimator Pro, knot count should be recorded as follows:
Super Fine*: 515 - 650 KPSI
Extremely Fine*: 415 - 510 KPSI
Very Fine*: 320 - 410 KPSI
Fine*: 224 - 315 KPSI
Very Good*: 131 - 220 KPSI
Good*: 99 - 130 KPSI
Coarse*: 56 - 96 KPSI
Very Coarse*: 36-54 KPSI
In the images below, the red dots with green stripes through them are counting the knots vertically and horizontally. KPSI is a result of multiplying the vertical knot count in one inch times the horizontal knot count in one inch.
For the rug below, what may appear to be two knots is actually a double
Knot count is always taken from the reverse side of the carpet. Flip your carpet over so the face of the rug is down, and the knots on back are exposed. You will need both a standard U.S. or Canadian quarter, a paper clip (to help point to knots so you do not lose place) and plenty of light. Begin counting the amount of knots in 1 inch left to right (horizontally known as the weft) and up and down (vertical: aka warp.) As you can see in the photographs below, a quarter is roughly 1" x 1". You may find it easier to follow a pattern or design in the rug, as many similar and adjacent colors tend to blend knots.
Once you have both the knot count of the rise and run, multiply them together, and you will come up with your KPSI. For best results, KPSI should be measured in 3 or more areas to find an average, as some rugs have KPSI which vary significantly.
*Bear in mind, the knot count descriptions of "very coarse" to "super fine" are only relative references. What may be a coarse knot count for a "city rug" may be considered "very fine" by tribal rug standards.
For additional information or one on one assistance please refer to our Rug Forum.