BRITISH STANDARD PIPE PARALLEL / BRITISH STANDARD PIPE TAPER
55 Degree Threads
| SIZE | TPI | MAJOR (EXT) | MINOR (INT) | TAP DRILL |
| 1/8" | 28 | 9.728 | 8.566 | 8.70 |
| 1/4" | 19 | 13.157 | 11.445 | 11.60 |
| 3/8" | 19 | 16.662 | 14.950 | 15.00 |
| 1/2" | 14 | 20.955 | 18.631 | 19.00 |
| 5/8" | 14 | 22.911 | 20.587 | 20.75 |
| 3/4" | 14 | 26.441 | 24.117 | 24.50 |
| 7/8" | 14 | 30.201 | 27.877 | 28.00 |
| 1" | 11 | 33.249 | 31.770 | 30.50 |
| 11/8" | 11 | 37.897 | 34.939 | 35.00 |
| 11/4" | 11 | 41.910 | 38.952 | 39.50 |
| 13/8" | 11 | 44.323 | 41.365 | 41.50 |
| 11/2" | 11 | 47.803 | 44.845 | 45.00 |
| 13/4" | 11 | 53.746 | 50.788 | 51.00 |
| 2" | 11 | 59.614 | 56.656 | 57.00 |
| 21/4" | 11 | 65.710 | 62.752 | 63.00 |
| 21/2" | 11 | 75.184 | 72.226 | 72.50 |
| 23/4 | 11 | 81.534 | 78.576 | 79.00 |
| 3" | 11 | 87.884 | 84.926 | 85.50 |
| 31/4" | 11 | 93.980 | 91.501 | 91.00 |
| 31/2" | 11 | 100.330 | 97.372 | 97.75 |
| 33/4" | 11 | 106.680 | 103.722 | 104.00 |
| 4" | 11 | 113.030 | 110.072 | 110.50 |
| 41/2" | 11 | 125.730 | 122.772 | 123.00 |
| 5" | 11 | 138.430 | 135.472 | 136.00 |
| 51/2" | 11 | 151.130 | 148.172 | 148.50 |
| 6" | 11 | 163.830 | 160.872 | 161.50 |
NOTE: G = BSPP / R = BSPT