National Pipe Thread Taper is the common American National Pipe Taper Threads.
NPT aliases are also known as:
- Male Pipe Thread (MPT or MNPT)
- Female Pipe Thread (FNPT or NPTF)
- Note: FPT & MPT are not authorized ANSI standards.
NOTE: Pipe sizes do not refer to its physical dimensions; the outside diameter of a pipe or fitting should be measured and compared with NPT chart or table like the one below:
| NPT – American Standard Pipe Thread Taper |
||||||
| Pipe Size (inches) |
Threads per Inch TPI – pitch |
Approximate Length of Thread (inches) |
Approximate Number of Threads to be Cut | Approximate Total thread Makeup, Hand and Wrench (inches) |
Nominal Outside Pipe Diameter OD (inches) |
Tap Drill (inches) |
| 1/16″ | 27 | 0.313 | ||||
| 1/8″ | 27 | 3/8 | 10 | 1/4 | 0.405 | R |
| 1/4″ | 18 | 5/8 | 11 | 3/8 | 0.540 | 7/16 |
| 3/8″ | 18 | 5/8 | 11 | 3/8 | 0.675 | 37/64 |
| 1/2″ | 14 | 3/4 | 10 | 7/16 | 0.840 | 23/32 |
| 3/4″ | 14 | 3/4 | 10 | 1/2 | 1.050 | 59/64 |
| 1″ | 11-1/2 | 7/8 | 10 | 9/16 | 1.315 | 1-5/32 |
| 1-1/4″ | 11-1/2 | 1 | 11 | 9/16 | 1.660 | 1-1/2 |
| 1-1/2″ | 11-1/2 | 1 | 11 | 9/16 | 1.900 | 1-47/64 |
| 2″ | 11-1/2 | 1 | 11 | 5/8 | 2.375 | 2-7/32 |
| 2-1/2″ | 8 | 1 1/2 | 12 | 7/8 | 2.875 | 2-5/8 |
| 3″ | 8 | 1 1/2 | 12 | 1 | 3.500 | 3-1/4 |
| 3-1/2″ | 8 | 1 5/8 | 13 | 1 1/16 | 4.000 | 3-3/4 |
| 4″ | 8 | 1 5/8 | 13 | 1 1/16 | 4.500 | 4-1/4 |
| 4 1/2″ | 8 | 5.000 | 4-3/4 | |||
| 5″ | 8 | 1 3/4 | 14 | 1 3/16 | 5.563 | 5-9/32 |
| 6″ | 8 | 1 3/4 | 14 | 1 3/16 | 6.625 | 6-11/32 |
| 8″ | 8 | 1 7/8 | 15 | 1 5/16 | 8.625 | |
| 10″ | 8 | 2 | 16 | 1 1/2 | 10.750 | |
| 12″ | 8 | 2 1/8 | 17 | 1 5/8 | 12.750 | |
| 14″ | 8 | 14.000 | ||||
| 16″ | 8 | 16.000 | ||||
