NPT Thread Chart (National Pipe Taper)
Complete National Pipe Taper (NPT) thread chart: 19 sizes with OD, pitch, minor diameters, TPI, and tap drill sizes per ASME B1.20.1.
| Thread | TPI | OD (in) | E0 Pitch Ø (in) | Minor Ø at E0 (in) | Tap Drill |
|---|---|---|---|---|---|
| 1/16" NPT | 27 | 0.3125 | 0.27118 | 0.25327 | 15/64" (5.95 mm) |
| 1/8" NPT | 27 | 0.4050 | 0.36351 | 0.34560 | R (8.61 mm) |
| 1/4" NPT | 18 | 0.5400 | 0.47739 | 0.44929 | 7/16" (11.11 mm) |
| 3/8" NPT | 18 | 0.6750 | 0.61201 | 0.58391 | 37/64" (14.68 mm) |
| 1/2" NPT | 14 | 0.8400 | 0.75843 | 0.72235 | 23/32" (18.26 mm) |
| 3/4" NPT | 14 | 1.0500 | 0.96768 | 0.93160 | 59/64" (23.42 mm) |
| 1" NPT | 11.5 | 1.3150 | 1.21363 | 1.17062 | 1-5/32" (29.37 mm) |
| 1-1/4" NPT | 11.5 | 1.6600 | 1.55713 | 1.51912 | 1-1/2" (38.10 mm) |
| 1-1/2" NPT | 11.5 | 1.9000 | 1.79609 | 1.75808 | 1-47/64" (44.05 mm) |
| 2" NPT | 11.5 | 2.3750 | 2.27000 | 2.23199 | 2-7/32" (56.36 mm) |
| 2-1/2" NPT | 8 | 2.8750 | 2.71953 | 2.62300 | 2-5/8" (66.67 mm) |
| 3" NPT | 8 | 3.5000 | 3.34062 | 3.24409 | 3-1/4" (82.55 mm) |
| 3-1/2" NPT | 8 | 4.0000 | 3.83750 | 3.74097 | 3-3/4" (95.25 mm) |
| 4" NPT | 8 | 4.5000 | 4.33438 | 4.23785 | 4-1/4" (107.95 mm) |
| 5" NPT | 8 | 5.5630 | 5.39073 | 5.29420 | 5-1/4" (133.35 mm) |
| 6" NPT | 8 | 6.6250 | 6.44609 | 6.34956 | 6-5/16" (160.34 mm) |
| 8" NPT | 8 | 8.6250 | 8.43359 | 8.33706 | 8-5/16" (211.14 mm) |
| 10" NPT | 8 | 10.7500 | 10.54531 | 10.44878 | 10-7/16" (265.11 mm) |
| 12" NPT | 8 | 12.7500 | 12.53281 | 12.43628 | 12-7/16" (315.91 mm) |
E0 = hand-tight engagement pitch diameter per ASME B1.20.1. Taper: 1 in 16 on diameter (3/4"/ft).
E0 = hand-tight engagement pitch diameter per ASME B1.20.1. Taper: 1 in 16 on diameter (3/4"/ft).
E0 = hand-tight engagement pitch diameter per ASME B1.20.1. Taper: 1 in 16 on diameter (3/4"/ft).