NPT (National Pipe Thread):
American National Standard Taper Pipe Thread.
NPS (New Product Standard):
NPS is the abbreviation for New Product Technical Safety or New Product Standard, which is one of the North American pipe sizing standard systems for high and low pressure and temperature. Its pipe sizes are identified by two non-size numbers, the NPS in inches and the pipe schedule number (expressed as Sched. or Sch.)
NPT is an American sealing pipe thread with a 60-degree thread angle that is primarily used for pipe connections to provide a reliable seal.
NPS is primarily used to identify the size of the pipe, not the thread type. It is related to the outer diameter (OD) and wall thickness of the pipe, but does not directly indicate the OD or wall thickness. The specific value needs to be checked through the relevant standards (e.g. ASME standards B36.10M and B36.19M).
NPT marking:
usually in the form of “1/4NPT”, “3/4NPT”, etc., indicating the size of the thread.
| Pipe size | Thread number | Thread pitch | Thread height | Hand-tight engagement | Effective thread | |||||
| D | No. | P | h | Length | Threads | Diameter | Length | Threads | Diameter | |
| (inch) | (mm) | (no. / inch) | (inch) | inch | (L1, inch) | (no.) | (E1, inch) | (L2, inch) | (no.) | (E3, inch) |
| 3/8″ | 17.1 | 18 | 0.05556 | 0.04444 | 0.24 | 4.32 | 0.62701 | 0.4078 | 7.34 | 0.6375 |
| 1/2″ | 21.3 | 14 | 0.07143 | 0.05714 | 0.32 | 4.48 | 0.77843 | 0.5337 | 7.47 | 0.79178 |
| 3/4″ | 26.7 | 14 | 0.07143 | 0.05714 | 0.339 | 4.75 | 0.98887 | 0.5457 | 7.64 | 1.00178 |
| 1″ | 33.4 | 11.5 | 0.08696 | 0.06957 | 0.4 | 4.6 | 1.23863 | 0.6828 | 7.85 | 1.25631 |
| 1-1/4″ | 42.2 | 11.5 | 0.08696 | 0.06957 | 0.42 | 4.83 | 1.58338 | 0.7068 | 8.13 | 1.60131 |
| 1-1/2″ | 48.3 | 11.5 | 0.08696 | 0.06957 | 0.402 | 4.83 | 1.82234 | 0.7235 | 8.32 | 1.84131 |
| 2″ | 60.3 | 11.5 | 0.08696 | 0.06957 | 0.436 | 5.01 | 2.29627 | 0.7565 | 8.7 | 2.3163 |
| 2-1/2″ | 73 | 8 | 0.125 | 0.1 | 0.682 | 5.46 | 2.76215 | 1.1375 | 9.1 | 2.79063 |
| 3″ | 88.9 | 8 | 0.125 | 0.1 | 0.766 | 6.13 | 3.3885 | 1.2 | 9.6 | 3.41563 |
| 4″ | 114.3 | 8 | 0.125 | 0.1 | 0.844 | 6.75 | 4.38712 | 1.3 | 10.4 | 4.41563 |
| 5″ | 141.3 | 8 | 0.125 | 0.1 | 0.937 | 0.94 | 5.44929 | 1.4063 | 11.25 | 5.47863 |
| 6″ | 168.3 | 8 | 0.125 | 0.1 | 0.958 | 7.66 | 6.50597 | 1.5125 | 12.1 | 6.54063 |
NPT Size Chart
NPS marking:
Usually appears in the form of “NPS1/2”, “NPS2”, etc., indicating the pipe size.
| ANSI B1.20.1 – NPS – American National Standard Straight Pipe Threads | ||||
| Pipe Size | TPI | Pipe Diameter | Female Thread Inside Diameter | Tap Drill |
| (inches) | (inches) | (inches) | ||
| 1/8 | 27 | 0.405 | 0.34 | S |
| 1/4 | 18 | 0.54 | 0.47 | 29/64 |
| 3/8 | 18 | 0.675 | 0.59 | 19/32 |
| 1/2 | 14 | 0.84 | 0.75 | 47/64 |
| 3/4 | 14 | 1.05 | 0.97 | 15/16 |
| 1 | 11.5 | 1.315 | 1.2 | 1 3/16 |
| 1 1/4 | 11.5 | 1.66 | 1-55 | 1 33/64 |
| 1 1/2 | 11.5 | 1.9 | 1.79 | 1 3/4 |
| 2 | 11.5 | 2.375 | 2.26 | 2 7/32 |
| 2 1/2 | 8 | 2.875 | 2.71 | 2 21/32 |
| 3 | 8 | 3.5 | 3.33 | 3 9/32 |
| 3 1/2 | 8 | 4 | 3 25/32 | |
| 4 | 8 | 4.5 | 4 9/32 | |
| 4 1/2 | 8 | 5 | 4 25/32 | |
| 5 | 8 | 5.563 | 5 11/32 | |
| 6 | 8 | 6.625 | 6 13/32 | |
NPS Dimension Chart
Since NPT and NPS are similar in abbreviation and both involve pipe sizes and threads, they are easily confused. In reality, however, they represent completely different concepts.
The result:
NPT is concerned with the type of thread and its sealing performance, and NPS is concerned with the pipe sizing identification system; they are not the same.
