The number of stitches (tufts) per running inch of carpet usually is specified directly for tufted carpet, but is called rows per inch for woven carpet. The numerical product of tuft rows per inch of width multiplied by stitches per running inch is the number of tufts per square inch, or tuft density.

The classification system roughly defines what type of room each floor can be used in. Class 32, for instance, signifies that the floors in this class can be used for moderate commercial use, while class 33 signifies heavy commercial use.

Handily, household carpets in the UK are graded according to their durability: Light domestic – suitable for bedrooms. Medium domestic – suitable for dining rooms. General domestic – suitable for living rooms. Heavy domestic – suitable for stairs and hallways.