NPT Thread Chart
Complete NPT pipe thread chart: 19 sizes with OD, pitch, minor diameters, TPI, and tap drill sizes per ASME B1.20.1.
| Thread | TPI | OD (in) | Pitch Ø (in) | Minor Ø (in) | Tap Drill (mm) |
|---|---|---|---|---|---|
| 1/16" NPT | 27 | 0.3125 | 0.2884 | 0.2671 | 6.78 |
| 1/8" NPT | 27 | 0.405 | 0.3809 | 0.3596 | 9.13 |
| 1/4" NPT | 18 | 0.54 | 0.5039 | 0.4718 | 11.98 |
| 3/8" NPT | 18 | 0.675 | 0.6389 | 0.6068 | 15.41 |
| 1/2" NPT | 14 | 0.84 | 0.7936 | 0.7524 | 19.11 |
| 3/4" NPT | 14 | 1.05 | 1.0036 | 0.9624 | 24.44 |
| 1" NPT | 11.5 | 1.315 | 1.2585 | 1.2083 | 30.69 |
| 1-1/4" NPT | 11.5 | 1.66 | 1.6035 | 1.5533 | 39.45 |
| 1-1/2" NPT | 11.5 | 1.9 | 1.8435 | 1.7933 | 45.55 |
| 2" NPT | 11.5 | 2.375 | 2.3185 | 2.2683 | 57.62 |
| 2-1/2" NPT | 8 | 2.875 | 2.7938 | 2.7216 | 69.13 |
| 3" NPT | 8 | 3.5 | 3.4188 | 3.3466 | 85.0 |
| 3-1/2" NPT | 8 | 4 | 3.9188 | 3.8466 | 97.7 |
| 4" NPT | 8 | 4.5 | 4.4188 | 4.3466 | 110.4 |
| 5" NPT | 8 | 5.563 | 5.4818 | 5.4096 | 137.4 |
| 6" NPT | 8 | 6.625 | 6.5438 | 6.4716 | 164.38 |
| 8" NPT | 8 | 8.625 | 8.5438 | 8.4716 | 215.18 |
| 10" NPT | 8 | 10.75 | 10.6688 | 10.5966 | 269.15 |
| 12" NPT | 8 | 12.75 | 12.6688 | 12.5966 | 319.95 |