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National Standard Taper Pipe Threads Size NPT Chart

National Standard Taper Pipe Threads Size NPT Chart - Includes both External and internal Pipe Thread Data. The taper rate for all NPT threads is 1⁄16 (3⁄4 inch per foot) measured by the change of diameter (of the pipe thread) over distance. The angle between the taper and the center axis of the pipe is 1° 47'′ 24"″ (1.7899°). Commonly-used sizes are 1/⁄8, 1/⁄4, 3/⁄8, 1⁄/2, 3⁄/4, 1, 1 1⁄/4, 1 1⁄/2, and 2 inch, appearing on pipes and fittings by most U.S. suppliers. Sizes smaller than 1/⁄8 inch are occasionally used for compressed air, while sizes larger than 2 inches are uncommon, due to the use of alternative methods of joining that are used with these larger sizes. NPT is defined by ANSI/ASME standard B1.20.1.

Nominal Pipe Size is loosely related to the inside diameter of Schedule 40 pipe. Because of the pipe wall thickness, the actual diameter of the threads is larger than the NPS, considerably so for small NPS. Other schedules of pipe have different wall thickness but the OD (outer diameter) and thread profile remain the same, so the inside diameter of the pipe is therefore different from the nominal diameter.

Notes:

 

  • Reference ANSI/ASME B1.20.1-1983 (R1992)
  • Angle between sides of thread is 60 degrees.
  • Thread taper, is 3⁄4 inch per foot.
  • All units are in inches.
Outside Diameter Nominal Pipe Size Thread per Inch (Pitch) Thread Pitch Length, P Pitch Diameter at External Thread Start E0 Hand Tight Thread Engagement Length, L1 Diameter E1 Maximum Thread Engagement L2 Diameter E2
0.3125 1/16 27 0.03704 0.27118 0.160 0.28118 0.2611 0.28750
0.405 1/8 27 0.03704 0.36351 0.1615 0.37360 0.2639 0.38000
0.540 ¼ 18 0.05556 0.47739 0.2278 0.49163 0.4018 0.50250
0.675 3/5 18 0.05556 0.61201 0.240 0.62701 0.4078 0.63750
0.840 ½ 14 0.07143 0.75843 0.320 0.77843 0.5337 0.79179
1.050 ¾ 14 0.07143 0.96768 0.339 0.98887 0.5457 1.00179
1.315 1 11 ½ 0.08696 1.21363 0.400 1.23863 0.6828 1.25630
1.660 1 ¼ 11 ½ 0.08696 1.55713 0.420 1.58338 0.7068 1.60130
1.900 1 ½ 11 ½ 0.08696 1.79609 0.420 1.82234 0.7235 1.84130
2.375 20 11 ½ 0.08696 2.26902 0.436 2.29627 0.7565 2.31630
2.875 2 ½ 8 0.08696 2.71953 0.682 2.76216 1.1375 2.79062
3.500 3/5 8 0.12500 3.34062 0.766 3.38850 1.2000 3.41562
4.000 3 ½ 8 0.12500 3.83750 0.821 3.8881 1.2500 3.91562
4.500 4 8 0.12500 4.33438 0.844 4.38712 1.3000 4.41562
5.563 5 8 0.12500 5.39073 0.937 5.44929 1.4063 5.47862
6.625 6 8 0.12500 6.44609 0.958 6.50597 1.5125 6.54062
8.625 8 8 0.12500 8.43359 1.063 8.50003 1.7125 8.54062
10.750 10 8 0.12500 10.54531 1.210 10.62094 1.9250 10.66562
12.750 12 8 0.12500 12.53281 1.360 12.61781 2.1250 12.66562
14.000 14 8 0.12500 13.77500 1.562 13.87262 2.2500 13.91562
16.000 16 8 0.12500 15.76250 1.812 15.87575 2.4500 15.91562
18.000 18 8 0.12500 17.75000 2.000 17.87500 2.6500 17.91562
20.000 20 8 0.12500 19.73750 2.125 19.87031 2.8500 19.91562
24.000 24 8 0.12500 23.71250 2.375 23.86094 3.2500 32.91562

National Standard Taper Pipe Threads Size NPT Chart

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