American National pipe (NPT, NPS), Like British Standard Pipe (BSP), is designated by trade size, rather than actual diameter, as shown in the table below. NPT Thread – American Standard Taper Pipe Thread (ANSI/ASME B1.20.1), Taper 1:16 Thread Form Data – Basic Dimensions of American National Standard Taper Threads, NPT (National Pipe Tapered) There are two basic types of National pipe threads: NPT: National Pipe Taper NPS: National Pipe Straight NPT threads are also sometimes referred to as MIP (Male Iron Pipe) FIP (Female Iron Pipe) IPT (Iron Pipe Thread) FPT (Female Pipe Thread) MPT (Male Pipe Thread) Note that these references are somewhat casual, and might possibly be used in reference to NPS instead of NPT. Both NPT and NPS have the same thread angle, shape, and pitch (threads per inch). However, NPT threads are tapered and NPS threads are straight (parallel). Both threads have a 60° included angle and have flat peaks and valleys (this is a Sellers thread