NPT Pipe Threads Chart
| BASIC DIMENSIONS AND PITCH | ||||
|---|---|---|---|---|
| Nominal pipe size (in) | Pipe outside diameter (in) | TPI | Pitch (in) | Pitch diameter at hand-tight plane E1 (in) |
| 1/16 | 0.3125 | 27 | 0.03704 | 0.28118 |
| 1/8 | 0.4050 | 27 | 0.03704 | 0.37360 |
| 1/4 | 0.5400 | 18 | 0.05556 | 0.49163 |
| 3/8 | 0.6750 | 18 | 0.05556 | 0.62701 |
| 1/2 | 0.8400 | 14 | 0.07143 | 0.77843 |
| 3/4 | 1.0500 | 14 | 0.07143 | 0.98887 |
| 1 | 1.3150 | 11.5 | 0.08696 | 1.23863 |
| 1 1/4 | 1.6600 | 11.5 | 0.08696 | 1.58338 |
| 1 1/2 | 1.9000 | 11.5 | 0.08696 | 1.82234 |
| 2 | 2.3750 | 11.5 | 0.08696 | 2.25627 |
| 2 1/2 | 2.8750 | 8 | 0.12500 | 2.76126 |
| 3 | 3.5000 | 8 | 0.12500 | 3.38850 |
| 3 1/2 | 4.0000 | 8 | 0.12500 | 3.88881 |
| 4 | 4.5000 | 8 | 0.12500 | 4.38712 |
NPT uses a 1:16 diameter taper. Pipe size is nominal and is not the thread major diameter. The table shows basic reference dimensions from the cited legacy handbook; use the current ASME standard for gauging and production.