ANSI / ASME B1.20.1
BASIC DIMENSIONS OF AMERICAN NATIONAL STANDARD TAPER PIPE THREAD , NPT
| Normal Pipe Size | 1/16" | 1/8" | 1/4" | 3/8" | 1/2" | 3/4" | 1" | 1.1/2" | 1.1/4" | 2" | 2.1/2" | 3" | ||
| O.D. of Pipe (D) | 0.32 | 0.4 | 0.54 | 0.67 | 0.84 | 1.05 | 1.31 | 1.66 | 1.9 | 2.37 | 2.87 | 3.5 | ||
| Threads/inch (n) | 27 | 27 | 18 | 18 | 14 | 14 | 11.5 | 11.5 | 11.5 | 11.5 | 8 | 8 | ||
| Pitch Thread (P) | 0.04 | 0.04 | 0.06 | 0.06 | 0.07 | 0.07 | 0.09 | 0.09 | 0.09 | 0.09 | 0.12 | 0.12 | ||
| Pitch Diameter of External Thread (En) | 0.03 | 0.36 | 0.48 | 0.61 | 0.76 | 0.97 | 1.21 | 1.56 | 1.8 | 2.27 | 111 | 3.34 | ||
| Handtight Engagement | Length (L1) (2) | Inches | 0.16 | 0.16 | 0.23 | 0.24 | 0.32 | 0.34 | 0.4 | 0.42 | 0.42 | 0.43 | 0.68 | 0.77 |
| Thread | 4.32 | 4.36 | 4.1 | 4.32 | 4.48 | 4.75 | 4.6 | 4.83 | 4.83 | 5.01 | 5.46 | 6.13 | ||
| Ø (E1) (3) | 0.28 | 0.38 | 0.49 | 0.63 | 0.78 | 0.99 | 1.24 | 1.58 | 1.82 | 2.3 | 2.76 | 3.39 | ||
| Effective Thread. External | Length (L2) (4) | Inches | 0.26 | 0.26 | 0.4 | 0.4 | 0.53 | 0.55 | 0.68 | 0.71 | 0.72 | 0.76 | 1.14 | 1.2 |
| Thread | 7.05 | 7.12 | 7.23 | 7.34 | 7.47 | 7.64 | 7.85 | 8.13 | 8.32 | 8.7 | 9.1 | 9.6 | ||
| Effective Thread. External | Ø (E2) | 0.29 | 0.38 | 0.5 | 0.64 | 0.79 | 1 | 1.26 | 1.6 | 1.84 | 2.31 | 2.79 | 3.41 | |
| Length L1 Plane to L2 Plane External Thread (L2-L1) | Inches | 0.1 | 0.1 | 0.17 | 0.17 | 0.21 | 0.21 | 0.28 | 0.29 | 0.3 | 0.32 | 0.45 | 0.43 | |
| Thread | 2.73 | 2.76 | 3.13 | 3.02 | 2.99 | 2.89 | 3.25 | 3.3 | 3.49 | 3.69 | 3.64 | 3.47 | ||
| Wrench Makeup Length for internal Thread (5) | Length(L3) | Inches | 0.11 | 0.11 | 0.17 | 0.17 | 0.21 | 0.21 | 0.26 | 0.26 | 0.26 | 0.26 | 0.25 | 0.25 |
| Thread | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 2 | 2 | ||
| Ø (E3) | 0.26 | 0.36 | 0.47 | 0.6 | 0.74 | 0.95 | 1.2 | 1.54 | 1.78 | 2.25 | 2.7 | 3.32 | ||
| Vanish Thread | Inches | 0.13 | 0.13 | 0.19 | 0.19 | 0.25 | 0.25 | 0.3 | 0.3 | 0.3 | 0.3 | 0.43 | 0.43 | |
| Thread | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | ||
| Overall Length External Thread (L4) | 0.39 | 0.39 | 0.59 | 0.6 | 0.78 | 0.79 | 0.98 | 1 | 1.02 | 1.06 | 1.57 | 1.63 | ||
| Nominal Complete External Threads (5) | Length (L5) | 0.19 | 0.19 | 0.29 | 0.3 | 0.39 | 0.4 | 0.51 | 0.53 | 0.55 | 0.58 | 0.89 | 0.95 | |
| Ø (E5) | 0.28 | 0.37 | 0.49 | 0.63 | 0.78 | 0.99 | 1.24 | 1.59 | 1.83 | 2.3 | 111 | 3.4 | ||
| Height of Thread (h) | 0.03 | 0.03 | 0.04 | 0.04 | 0.06 | 0.06 | 0.07 | 0.07 | 0.07 | 0.07 | 0.1 | 0.1 | ||
| Increase in Ø / Thread (0.0625/n) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0.01 | 0.01 | ||
| Basic Minor Ø At Small End of Pipe (K0) | 0.24 | 0.33 | 0.43 | 0.57 | 0.7 | 0.91 | 1.14 | 1.49 | 1.72 | 2.19 | 2.62 | 3.24 | ||
| Normal Pipe Size | 3.1/2 " | 4” | 5” | 6” | 8” | 10” | 12” | 14” 0.D. | 16” 0.D. | 18” 0.D. | 20” 0.D. | 24” 0.D. | ||
| O.D. of Pipe (D) | 4 | 4.5 | 5.56 | 6.62 | 8.62 | 10.75 | 12.75 | 14 | 16 | 18 | 20 | 24 | ||
| Threads/inch (n) | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | ||
| Pitch Thread (P) | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | ||
| Pitch Diameter of External Thread (En) | 3.84 | 4.33 | 5.39 | 6.45 | 8.43 | 10.54 | 12.53 | 13.77 | 15.76 | 17.75 | 19.74 | 23.71 | ||
| Handtight Engagement | Length(L1) (2) | Inches | 0.82 | 0.84 | 0.94 | 0.96 | 1.06 | 1.21 | 1.36 | 1.56 | 1.81 | 2 | 2.12 | 2.37 |
| Thread | 6.57 | 6.75 | 7.5 | 7.66 | 8.5 | 9.68 | 10.88 | 12.5 | 14.5 | 16 | 17 | 19 | ||
| Ø (E1) (3) | 3.89 | 4.39 | 5.45 | 6.5 | 8.5 | 10.62 | 12.62 | 13.87 | 15.87 | 17.87 | 19.87 | 23.86 | ||
| Effective Thread. External | Length(L2) (4) | Inches | 1.25 | 1.3 | 1.41 | 1.51 | 1.71 | 1.92 | 2.12 | 2.25 | 2.45 | 2.65 | 2.85 | 3.25 |
| Thread | 10 | 10.4 | 11.25 | 12.1 | 13.7 | 15.4 | 17 | 18 | 19.6 | 21.2 | 22.8 | 26 | ||
| Ø (E2) | 3.91 | 4.41 | 6.47 | 6.54 | 8.54 | 10.66 | 12.66 | 13.91 | 15.91 | 17.91 | 19.91 | 23.91 | ||
| Length L1 Plane to L2 Plane External Thread (L2-L1) | Inches | 0.43 | 0.46 | 0.47 | 0.55 | 0.65 | 0.71 | 0.76 | 0.69 | 0.64 | 0.65 | 0.72 | 0.87 | |
| Thread | 3.43 | 3.65 | 3.75 | 4.44 | 5.2 | 5.72 | 6.12 | 5.5 | 5.1 | 5.2 | 5.8 | 7 | ||
| Wrench Makeup Length for internal Thread (5) | Length(L3) | Inches | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 |
| Thread | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | ||
| Ø (E3) | 3.82 | 4.32 | 5.37 | 6.43 | 8.42 | 10.53 | 12.52 | 13.76 | 15.75 | 17.34 | 19.72 | 23.7 | ||
| Vanish Thread | Inches | 0.43 | 0.43 | 0.43 | 0.43 | 0.43 | 0.43 | 0.43 | 0.43 | 0.43 | 0.43 | 0.43 | 0.43 | |
| Thread | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | 3.47 | ||
| Overall Length External Thread (L4) | 1.69 | 1.73 | 1.84 | 1.95 | 2.15 | 2.36 | 2.56 | 2.68 | 2.88 | 3.08 | 3.28 | 3.68 | ||
| Nominal Complete External Threads (5) | Length (L5) | 1 | 1.05 | 1.16 | 1.26 | 1.46 | 1.67 | 1.87 | 2 | 2.2 | 2.4 | 2.6 | 3 | |
| Ø (E5) | 3.9 | 4.4 | 5.46 | 6.52 | 8.52 | 10.65 | 12.65 | 13.9 | 15.9 | 17.9 | 19./90 | 23.9 | ||
| Height of Thread (h) | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | ||
| Increase in Ø / Thread (0.0625/n) | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | ||
| Basic Minor Ø At Small End of Pipe (K0) | 3.73 | 4.23 | 5.29 | 6.35 | 8.33 | 10.44 | 12.43 | 13.67 | 15.66 | 17.65 | 19.64 | 23.61 | ||
NOTES:
(1) The basic dimensions of the American National Standard Taper Pipe Thread are given in inches to four or five decimal
places. While this implies a greater degree of precision than is ordinarily attained, these dimensions are the basis of gauge dimensions and are so expressed for the purpose of eliminating errors in computations.
(2) Also length of thin ring gauge and length from gauging notch to small end of plug gauge.
(3) Also pitch diameter at gauging notch (handtight plane).
(4) Also length of plug gauge.
(5) The length L5from the end of the pipe determines the plane beyond which the thread form is incomplete at the crest. The next two threads are complete at the root. At this plane the cone formed by the crests of the thread intersects the cylinder forming the external surface of the pipe. L5 = L2 - 2p.
(6) Given as information for use in selecting tap drills. (See Appendix).
(7) Military Specification MIL-P-7105 gives the wrench makeup as three threads for sizes 3 and smaller. The E3 dimensions are as follows: Nominal pipe size 2.1/2 = 2.69609 and size 3 = 3.31719; size 2 and smaller same as above, col. 16.
(8) Reference dimension