NPT Pipe Thread (USA)

The NPT thread is part of the American National Standard Pipe Thread and is included in the American system of pipe threads used for pipes and fittings of all kinds. NPT stands for National pipe taper; the full name of the thread is American National Standard Taper Pipe Thread. The term "taper" describes the conical shape of the NPT thread. The NPT thread is standardized according to ANSI B 1.20.1-1983 (R1992). The standard is monitored by the American National Standards Institute (ANSI). The NPT thread is a universal pipe thread that can be used for almost all connections. It is combined with other pipe thread profiles for certain applications.

The NPT thread is a tapered pipe thread with a taper of 1:16 and a flank angle of 60°. It is an inch thread with dimensions in inches and a pitch expressed in threads per inch. The NPT thread is not mechanically sealing and must therefore be used in combination with a sealing compound. For use, either an NPT external thread is combined with an NPT internal thread, or an NPT external thread is combined with an NPSC internal thread.

The thread designation consists of an inch value, the pitch in threads per inch, and the abbreviation NPT. Therefore, a correct thread identification would be, for example, 3/4″ – 14 NPT. As with all pipe threads, it is important to note that the inch specification in the thread designation does not correspond to the actual external diameter. This is due to changes in pipe geometry over the past century, which have not affected the thread designations. Therefore, the 1″ – 11 1/2 NPT has an external diameter of 1.308 inches or 33.228 mm.

The thread table for the NPT pipe thread includes dimensions from 1/16″ – 27 NPT up to 12″ – 8 NPT. In addition to the external diameter and pitch, the required core hole diameter at the thin pipe end is also listed. If you need dies or taps for the NPT thread, simply follow the links in the table.