National Pipe Tapered (NPT)：
is a type of pipe thread produced in accordance with the American Standard ANSI B1.20.1, also known as the American Standard Pipe Thread.The main feature of NPT threads is their tapered design, which allows the threads to form a tight seal when connected to prevent leakage.NPT threads are used in a wide variety of piping systems, especially in applications where high pressure and fluid transfer reliability are required. NPT threads are widely used in a variety of piping systems, especially where high pressures and fluid transfer reliability are required.
Below is a chart of NPT dimensions：
All units are in inches.
| 0utside Diameter D | Nominal Pipe Size | Threads per lnch (Pitch) | Thread Pitah Length P | Pitah Diameter at Extemal 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 | 1⁄4 | 18 | 0.05556 | 0.47739 | 0.2278 | 0.49163 | 0.4018 | 0.50250 |
| 0.675 | 3⁄8 | 18 | 0.05556 | 0.61201 | 0.240 | 0.62701 | 0.4078 | 0.63750 |
| 0.840 | 1⁄2 | 14 | 0.07143 | 0.75843 | 0.320 | 0.77843 | 0.5337 | 0.79179 |
| 1.050 | 3⁄4 | 14 | 0.07143 | 0.96768 | 0.339 | 0.98887 | 0.5457 | 1.00179 |
| 1.315 | 1 | 11 1/2 | 0.08696 | 1.21363 | 0.400 | 1.23863 | 0.6828 | 1.25630 |
| 1.660 | 1 1/4 | 11 1/2 | 0.08696 | 1.55713 | 0420 | 1.58338 | 0.7068 | 1.60130 |
| 1.900 | 1 1/2 | 11 1/2 | 0.08696 | 1.79609 | 0.420 | 1.82234 | 0.7235 | 1.84130 |
| 2.375 | 2 | 11 1/2 | 0.08696 | 2.26902 | 0.436 | 2.29627 | 0.7565 | 2.31630 |
| 2875 | 2 1/2 | 8 | 0.12500 | 2.71953 | 0.682 | 2.76216 | 1.1375 | 2.79062 |
| 3.500 | 3 | 8 | 0.12500 | 3.3406 | 0.766 | 3.38850 | 1.2000 | 3.41562 |
| 4.000 | 3 1/2 | 8 | 0.12500 | 3.83750 | 0.821 | 3.88881 | 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 | 23.91562 |
