Previous Term Next Term Stitches Per Inch (SPI) Stitches per inch (SPI), or tufts per inch, refers to the number of yarn tufts in one inch that run along the length of a tufted carpet. In woven carpet, this is referred to as rows per inch (RPI). Sources Carpet and Rug Institute (CRI) Related Terms Fumed Wood Shirred Drapery Header Accordion Pleat Pencil Pleat Photochromic Flat Pleat Materials CarpetFlooring Was this insightful? Yes No