A Tabriz rug/carpet is a type of Persian rug from the area of Tabriz. Tabriz is one of the major cities of Iran, and the capital city of East Azarbaijan Province of Iran.Most of its population are Azerbaijanis. It is one of the oldest rug weaving centers and makes a huge diversity of types of carpets. The range starts at Bazaar quality of 24 raj (Number of knots per length of 7cm of the widths of the rug) and on up to the incredibly fine 110 raj. Raj are the units of knot density (it showes the finess of the rug which based on the number of strings used for the fundation of the rug. Strigs materials are usualy made of cotton or silk which is used for very fine rugs). This method used primarily in Iran typically for Tabriz Rugs. However, Raj has been known as a point in reference for other carpets as well. It is originally believed that this unit of measure was derived from comparing the length of one standard rolled cigarette to the knots on the reverse of a rug.

The way to determine KPSI (Knots Per Square Inch) from RAJ is as follows: ((RAJ/7)*2.54)^2=KPSI