Here Is A Chart That Shows All of the Pipe thread Sizes and Threads Per inch Tpi: NPT Fittings (Click Here)Pipe Thread Size:Threads Per Inch:Theoretical I.D. Closest AN Size:1/16271/16-1/8271/841/4181/463/8183/8 81/2141/2103/4143/412111-1/21161-1/411-1/21-1/4201-1/211-1/21-1/224211-1/2232 … read more