Basic Dimensions, American National Standard Taper Pipe Threads, NPT, (ANSI B2.1-1968)

 




***All dimensions are given in inches***

Nominal Pipe Size
Outside Diameter of Pipe
Threads per Inch
Pitch of Thread
Pitch Diameter at Beginning of External Thread
Handtight Engagement
Effective Thread, External
Wrench Makeup Length for Internal Thread
Vanish Thread
Overall Length External Thread
Nominal Perfect External Threads
Height of Thread
Basic Minor Diameter at Small End of Pipe
Length
Diameter
Length
Diameter
Length

-
Diameter
Length
Diameter
See Note        
See Note        
See Note        
-
See Note
-
-
-
-
< 2 >
< 3 >
< 4 >
-
< 7 >
-
-
-
-
See Note
In.
-
In.
-
-
-
-
-
-
< 6 >
-
(D)
(n)
(p)
(Eo)
(L1)
(E1)
(L2)
(E2)
(L3)
-
(E3)
(V)
(L4)
(L5)
(E5)
(h)
(Ko)
1/16
0.313
27
0.03704
0.27118
0.1600
0.28118
0.2611
0.28750
0.1111
-
0.26424
0.1285
0.3896
0.1870
0.28287
0.02963
0.2416
1/8
0.405
27
0.03704
0.36351
0.1615
0.37360
0.2639
0.38000
0.1111
-
0.35656
0.1285
0.3924
0.1898
0.37537
0.02963
0.3339
1/4
0.540
18
0.05556
0.47739
0.2278
0.49163
0.4018
0.50250
0.1667
-
0.46697
0.1928
0.5946
0.2907
0.49556
0.04444
0.4329
3/8
0.675
18
0.05556
0.61201
0.2400
0.62701
0.4078
0.63750
0.1667
-
0.60160
0.1928
0.6006
0.2967
0.63056
0.04444
0.5676
1/2
0.840
14
0.07143
0.75843
0.3200
0.77843
0.5337
0.79179
0.2143
-
0.74504
0.2478
0.7815
0.3909
0.78286
0.05714
0.7013
3/4
1.050
14
0.07143
0.96768
0.3390
0.98887
0.5457
1.00179
0.2143
-
0.95492
0.2478
0.7935
0.4029
0.99286
0.05714
0.9105
1
1.315
11 1/2
0.08696
1.21363
0.4000
1.23863
0.6828
1.25630
0.2609
-
1.19733
0.3017
0.9845
0.5089
1.24543
0.06957
1.1441
1 1/4
1.660
11 1/2
0.08696
1.55713
0.4200
1.58338
0.7068
1.60130
0.2609
-
1.54083
0.3017
1.0085
0.5329
1.59043
0.06957
1.4876
1 1/2
1.900
11 1/2
0.08696
1.79609
0.4200
1.82234
0.7235
1.84130
0.2609
-
1.77978
0.3017
1.0252
0.5496
1.83043
0.06957
1.7265
2
2.375
11 1/2
0.08696
2.26902
0.4360
2.29627
0.7565
2.31630
0.2609
-
2.25272
0.3017
1.0582
0.5826
2.30543
0.06957
2.1995
2 1/2
2.875
8
0.12500
2.71953
0.6820
2.76216
1.1375
2.79062
0.2500
See Note < 8 >
2.70391
0.4337
1.5712
0.8875
2.77500
0.1
2.6195
3
3.500
8
0.12500
3.34062
0.7660
3.38850
1.2000
3.41562
0.2500
See Note < 8 >
3.32500
0.4337
1.6337
0.9500
3.40000
0.1
3.2406
3 1/2
4.000
8
0.12500
3.83750
0.8210
3.88881
1.2500
3.91562
0.2500
-
3.82188
0.4337
1.6837
1.0000
3.90000
0.1
3.7375
4
4.500
8
0.12500
4.33438
0.8440
4.38712
1.3000
4.41562
0.2500
-
4.31875
0.4337
1.7337
1.0500
4.40000
0.1
4.2344
5
5.563
8
0.12500
5.39073
0.9370
5.44929
1.4063
5.47862
0.2500
-
5.37511
0.4337
1.8400
1.1563
5.46300
0.1
5.2907
6
6.625
8
0.12500
6.44609
0.9580
6.50597
1.5125
6.54062
0.2500
-
6.43047
0.4337
1.9462
1.2625
6.52500
0.1
6.3461
8
8.625
8
0.12500
8.43359
1.0630
8.50003
1.7125
8.54062
0.2500
-
8.41797
0.4337
2.1462
1.4625
8.52500
0.1
8.3336
10
10.750
8
0.12500
10.54531
1.2100
10.62094
1.9250
10.66562
0.2500
-
10.52969
0.4337
2.3587
1.6750
10.65000
0.1
10.4453

Note < 1 >

The basic dimension of the ANSI standard taper pipe thread are given in inches to four or five decimal places. While this implies a greater degree of precision than is ordinarily attained, these dimensions are the basis of gage dimensions and are so expressed for the purpose of eliminating errors in computations.

Note < 2 >

Also length of thin ring gage and length from gaging notch to small end of plug age.

Note < 3 >

Also pitch diameter at gaging notch (handtight plane).

Note < 4 >

Also length of plug gage.

Note < 5 >

The length L5 from the end of the pipe determines the plane beyond which the thread form is imperfect at the crest. The next tow threads are perfect at the root. At this plane the cone formed by the crests of the thread intersects the cylinder forming the external surface of the pipe. L5=L2-2p

Note < 6 >

Given as information for use in selecting tap drills.

Note < 7 >

Three threads for 2-inch size and smaller; two threads for larger sizes.

Note < 8 >

Military Specification MIL-P-7105 gives the wrench makeup as three threads for 3 in. and smaller. The E3 dimensions are then as follows: Size 2 1/2 in., 2.69609 and size 3 in., 3.31719. Increase in diameter per thread is equal to 0.0625/n.