American National Standard Pipe Thread standards, often called national pipe thread standards for short, are U.S. national technical standards for screw threads used on threaded pipes and pipe fittings. They include both tapered and straight thread series for various purposes including rigidity, pressure-tight sealing, or both.[1] The various types are each named with a symbol and a full name; examples of the symbols include NPT, NPS, NPTF, NPSC, and others.
MIP is an acronym for male iron pipe, and FIP is an acronym for female iron pipe.[2]
Outside the United States, some US pipe threads are found, as well as many British Standard Pipe threads and ISO 7-1, 7-2, 228-1, and 228-2 threads.
The various types are each named with a symbol and a full name, as follows:[3]
| Abbreviation[3] | Shorthand expansion | Full name[3] | Comment[3] |
|---|---|---|---|
| NPT | National pipe taper | American National Standard Taper Pipe Thread | Tapered for sealing, often without any thread sealant; for connections in nearly every type of service |
| NPS | National pipe straight | American National Standard Straight Pipe Thread | For rigidity; sealable only with sealant; sometimes male straight enclosed by female tapered for low-pressure sealing |
| NPSC | National pipe straight–coupling | American National Standard Straight Pipe Thread for Couplings | For general couplings |
| NPSF | National pipe straight–fuel | Dryseal USA (American) Standard Fuel Internal Straight Pipe Thread | Internal only, straight |
| NPSH | National pipe straight–hose | American National Standard Straight Pipe Thread for Hose Couplings | For hose couplings |
| NPSI | National pipe straight–intermediate | Dryseal USA (American) Standard Intermediate Internal Straight Pipe Thread | Similar to NPSF but slightly larger; internal only, straight |
| NPSL | National pipe straight–locknut | American National Standard Straight Pipe Thread for Loose-fitting Mechanical Joints with Locknuts | For use with locknuts |
| NPSM | National pipe straight–mechanical | American National Standard Straight Pipe Thread for Free-fitting Mechanical Joints | For various rigid mechanical uses |
| NPTF | National pipe taper–fuel | Dryseal USA (American) Standard Taper Pipe Thread | For dryseal connections in nearly every type of service, especially fuel connections |
| NPTR | National pipe taper–railing | American National Standard Taper Pipe Thread for Railing Joints | For railings |
| PTF-SAE SHORT | Pipe taper, fuel, SAE, short | Dryseal SAE Short Taper Pipe Thread | Named after SAE International; similar to NPTF but one turn shorter |
American Society of Mechanical Engineers National Pipe Thread Taper (NPT)
|
Nominal
pipe size
|
Thread
density
|
Thread pitch | Hand-tight engagement[7] | Effective thread[7] | Overall | Actual outside | Tap drill | |||||||
| Length | Turns | Diameter | Length | Turns | Diameter | length[7] | diameter, OD | |||||||
| inch | inch−1 | inch | mm | inch | inch | inch | inch | inch | inch | mm | inch | mm | ||
| 1⁄16 | 27 | 0.037037 | 0.9407 | 0.16 | 4.32 | 0.28118 | 0.2611 | 7.05 | 0.2875 | 0.3896 | 0.313 | 7.95 | ||
| 1⁄8 | 27 | 0.037037 | 0.9407 | 0.1615 | 4.36 | 0.3736 | 0.2639 | 7.13 | 0.38 | 0.3924 | 0.405 | 10.287 | 0.339 | 8.6106 |
| 1⁄4 | 18 | 0.0555556 | 1.4111 | 0.2278 | 4.1 | 0.49163 | 0.4018 | 7.23 | 0.5025 | 0.5946 | 0.54 | 13.716 | 7⁄16 | 11.113 |
| 3⁄8 | 18 | 0.0555556 | 1.4111 | 0.24 | 4.32 | 0.62701 | 0.4078 | 7.34 | 0.6375 | 0.6006 | 0.675 | 17.145 | 37⁄64 | 14.684 |
| 1⁄2 | 14 | 0.0714286 | 1.8143 | 0.32 | 4.48 | 0.77843 | 0.5337 | 7.47 | 0.79178 | 0.7815 | 0.84 | 21.336 | 23⁄32 | 18.2563 |
| 3⁄4 | 14 | 0.0714286 | 1.8143 | 0.339 | 4.75 | 0.98887 | 0.5457 | 7.64 | 1.00178 | 0.7935 | 1.05 | 26.67 | 59⁄64 | 23.4156 |
| 1 | 11 1⁄2 | 0.0869565 | 2.2087 | 0.4 | 4.6 | 1.23863 | 0.6828 | 7.85 | 1.25631 | 0.9845 | 1.315 | 33.401 | 1 5⁄32 | 29.3688 |
| 1 1⁄4 | 11 1⁄2 | 0.0869565 | 2.2087 | 0.42 | 4.83 | 1.58338 | 0.7068 | 8.13 | 1.60131 | 1.0085 | 1.66 | 42.164 | 1 1⁄2 | 38.1 |
| 1 1⁄2 | 11 1⁄2 | 0.0869565 | 2.2087 | 0.42 | 4.83 | 1.82234 | 0.7235 | 8.32 | 1.84131 | 1.0252 | 1.9 | 48.26 | 1 47⁄64 | 44.0531 |
| 2 | 11 1⁄2 | 0.0869565 | 2.2087 | 0.436 | 5.01 | 2.29627 | 0.7565 | 8.7 | 2.3163 | 1.0582 | 2.375 | 60.325 | 2 7⁄32 | 56.3563 |
| 2 1⁄2 | 8 | 0.125 | 3.175 | 0.682 | 5.46 | 2.76216 | 1.1375 | 9.1 | 2.79063 | 1.5712 | 2.875 | 73.025 | 2 5⁄8 | 66.675 |
| 3 | 8 | 0.125 | 3.175 | 0.766 | 6.13 | 3.3885 | 1.2 | 9.6 | 3.41563 | 1.6337 | 3.5 | 88.9 | 3 1⁄4 | 82.55 |
| 3 1⁄2 | 8 | 0.125 | 3.175 | 0.821 | 6.57 | 3.88881 | 1.25 | 10 | 3.91563 | 1.6837 | 4 | 101.6 | 3 3⁄4 | 95.25 |
| 4 | 8 | 0.125 | 3.175 | 0.844 | 6.75 | 4.38713 | 1.3 | 10.4 | 4.41563 | 1.7337 | 4.5 | 114.3 | 4 1⁄4 | 107.95 |
| 4 1⁄2 | 8 | 0.125 | 3.175 | 5 | 127 | 4 3⁄4 | 120.65 | |||||||
| 5 | 8 | 0.125 | 3.175 | 0.937 | 7.5 | 5.44929 | 1.4063 | 11.25 | 5.47863 | 1.84 | 5.563 | 141.3002 | 5 9⁄32 | 134.1438 |
| 6 | 8 | 0.125 | 3.175 | 0.958 | 7.66 | 6.50597 | 1.5125 | 12.1 | 6.54063 | 1.9462 | 6.625 | 168.275 | 6 11⁄32 | 161.1313 |
| 8 | 8 | 0.125 | 3.175 | 1.063 | 8.5 | 8.50003 | 1.7125 | 13.7 | 8.54063 | 2.1462 | 8.625 | 219.075 | ||
| 10 | 8 | 0.125 | 3.175 | 1.21 | 9.68 | 10.62094 | 1.925 | 15.4 | 10.66563 | 2.3587 | 10.75 | 273.05 | ||
| 12 | 8 | 0.125 | 3.175 | 1.36 | 10.88 | 12.61781 | 2.125 | 17 | 12.66563 | 2.5587 | 12.75 | 323.85 | ||
| 14 | 8 | 0.125 | 3.175 | 1.562 | 12.5 | 13.87263 | 2.25 | 18 | 13.91563 | 2.6837 | 14 | 355.6 | ||
| 16 | 8 | 0.125 | 3.175 | 1.812 | 14.5 | 15.87575 | 2.45 | 19.6 | 15.91563 | 2.8837 | 16 | 406.4 | ||
| 18 | 8 | 0.125 | 3.175 | 2 | 16 | 17.875 | 2.65 | 21.2 | 17.91563 | 3.0837 | 18 | 457.2 | ||
| 20 | 8 | 0.125 | 3.175 | 2.125 | 17 | 19.87031 | 2.85 | 22.8 | 19.91563 | 3.2837 | 20 | 508 | ||
| 24 | 8 | 0.125 | 3.175 | 2.375 | 19 | 23.86094 | 3.25 | 26 | 23.91563 | 3.6837 | 24 | 609.6 | ||
