American Pipe Threads
Basic Dimensions, American Standard Taper Pipe Threads, NPT
For all dimensions see corresponding reference letters in table. Angle between sides of thread is 60 degrees. Taper of thread, on diameter, is 3/4 inch per foot. Angle of taper with centerline is 1° 47'. The basic maximum thead height, h of the truncated thread is 0.8 x pitch of thread. The crest and root are truncated a minimum of 0.033 x pitch for all pitches.
Nominal Pipe Size |
Outside Diameter of Pipe, D |
Threads per Inch, n |
Pitch of Thread, p |
Pitch Dia. at Beginning of External Thread
E0
E0
Handtight Engagement |
Length In., L1 |
Diameter, E1 |
Effective Thread External |
Length In., L2 |
Diameter, E2 |
1/16
0.3125
27
0.03704
0.27118
0.160
0.28118
0.2611
0.28750
1/8
0.405
27
0.03704
0.36351
0.1615
0.37360
0.2639
0.38000
1/4
0.540
18
0.05556
0.47739
0.2278
0.49163
0.4018
0.50250
3/8
0.675
18
0.05556
0.61201
0.240
0.62701
0.4078
0.63750
1/2
0.840
14
0.07143
0.75843
0.320
0.77843
0.5337
0.79179
3/4
1.050
14
0.07143
0.96768
0.339
0.98887
0.5457
1.00179
1
1.315
11-1/2
0.08696
1.21363
0.400
1.23863
0.6828
1.25630
1-1/4
1.660
11-1/2
0.08696
1.55713
0.420
1.58338
0.7068
1.60130
1-1/2
1.900
11-1/2
0.08696
1.79609
0.420
1.82234
0.7235
1.84130
2
2.375
11-1/2
0.08696
2.26902
0.436
2.29627
0.7565
2.31630
2-1/2
2.875
8
0.12500
2.71953
0.682
2.76216
1.1375
2.79062
3
3.5
8
0.12500
3.34062
0.766
3.38850
1.2000
3.41562
3-1/2
4
8
0.12500
3.83750
0.821
3.88881
1.2500
3.91562
4
4.5
8
0.12500
4.33438
0.844
4.38712
1.3000
4.41562
5
5.563
8
0.12500
5.39073
0.937
5.44929
1.4063
5.47862
6
6.625
8
0.12500
6.44609
0.958
6.50597
1.5125
6.54062
8
8.625
8
0.12500
8.43359
1.063
8.50003
1.7125
8.54062
10
10.750
8
0.12500
10.54531
1.210
10.62094
1.9250
10.66562
12
12.750
8
0.12500
12.53281
1.360
12.61781
2.1250
12.66562