Face weight is determined by the amount of fiber in one square yard of carpet.
Face Weight or Ounces
Yarn Ply- twist
Turns per inch, the number of times two or more yarns have been piled or twisted is measured in the length of one inch. The performance of cut pile carpet is influenced most by the twist in the pile yarn.
Density
The amount of pile packed into a given volume of carpet. Density is a product of the stitch rate, gauge, yarn weight and size.
Stitches per inch
Just as the gauge controls the frequency of the tufts across the width, stitches per inch defines the number of stitches sewn by the needles down the length of the carpet. The stitch rate is controlled by the speed at which the primary backing is fed through the tufting machine. A generally accepted rule of thumb is that the stitches per inch should roughly equal the number of needles per inch in the in the gauge.
Pile Height
Pile height is the length of the tuft from the backing surface, or bottom of the carpet face, to the tip of the yarn tuft. It is measured as a fraction of an inch or as a decimal equivalent. Increasing or decreasing the pile height can affect the performance.