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