NPT-National Pipe Thread Chart Common American National Standard Pipe Taper Threads • NPT - National Pipe Thread Taper • NPTF - Dryseal American National Standard Taper Pipe Thread (ANSI B1.20.3) NPT Threads may be referred to as MPT (Male Pipe Thread), MNPT, or NPT(M) for male external threads, and FPT (Female Pipe Thread*), FNPT, or NPT(F) for female (internal) threads. Note that FPT and MPT are not authorized designations per the ANSI standard. For NPT threads a sealant compound or Polytetrafluoroethylene (PTFE) tape must be used for leak-free seal. For NPTF no sealant is needed for a leak tight connection. Characteristics of NPT (also known as ANSI/ASME B1.20 1 Pipe Threads, General Purpose): • the angle between the taper and center axis of the pipe is 1° 47’ 24” (1.7899°) • truncation of roots and crests are flat • 60° thread angle • pitch is measured in threads per inch Pipe size do not refer to any physical dimensions. The outside diameter of a pipe or fitting must be measured and compared to a table for size identification. A 3/4” NPT pipe thread has an outside diameter -OD - of 1.050 inches. Each thread size has a defined number of threads per inch - TPI, or pitch. The 3/4” NPT pipe thread has 14 threads per inch. Both the TPI and OD of the thread are required for positive identification of thread size because more than one size have the same TPI. NPT - American Standard Pipe Thread Chart Pipe Size (Inches) Thread per Inch TPI - Approximate Length of Approximate Number Approximate Total Nominal Outside Pipe Tap Drill (Inches) pitch Thread (Inches) of Threads to be Cut thread make up. Hand Diameter OD (Inches) and Wrench (Inches) (mm) 1/16” 27 0.313 1/8” 27 3/8 10 1/4 0.405 R 1/4” 18 5/8 11 3/8 0.540 7/16 3/8” 18 5/8 11 3/8 0.675 37/64 1/2” 14 3/4 10 7/16 0.840 23/32 3/4” 14 3/4 10 1/2 1.050 59/64 1” 11-1/2 7/8 10 9/16 1.315 1-5/32 1-1/4” 11-1/2 1 11 9/16 1.660 1-1/2 1-1/2” 11-1/2 1 11 9/16 1.900 1-47/64 2” 11-1/2 1 11 5/8 2.375 2-7/32 2-1/2” 8 1 1/2 12 7/8 2.875 2-5/8 3” 8 1 1/2 12 1 3.500 3-1/4 3-1/2” 8 1 5/8 13 1 1/16 4.000 3-3/4 4” 8 1 5/8 13 1 1/16 4.500 4-1/4 4 1/2” 8 5.000 4-3/4 5” 8 1 3/4 14 1 3/16 5.563 5-9/32 6” 8 1 3/4 14 1 3/16 6.625 6-11/32 8” 8 1 7/8 15 1 5/16 8.625 10” 8 2 16 1 1/2 10.750 12” 8 21/8 17 1 5/8 12.750 14” 8 14.000 16” 8 16.000 1) The taper rate is 1 in 16 inch (3/4 inch in a foot 62.5 mm in a meter) • 1 inch = 25.4 mm NPT threads are not interchangeable with NPS - National Pipe Straight- threads. NPT threads may look similar to ISO 7/1 threads. However, ISO and NPT threads should not be mixed. ISO threads have 55° taper angle versus 60° for NPT. The NPT root and crest configurations are also different from ISO. Fox ISO threads pitch is usually measured in millimeters (may be expressed in Inch). The pitch are different. Patlin has made a concerted effort to provide accurate information, however Patlin assumes no responsibility for the accuracy of the information. Printed in U.S.A. Connect with us on: 855.728.5460 www.patlininc.com.