Standard Taper Pipe Threads NPT Basic Dimensions, American National Standard

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Standard Taper Pipe Threads NPT Basic Dimensions, American National Standard

Basic Dimensions, American National Standard Taper Pipe Threads, NPT

Notes:

Reference ANSI/ASME B1.20.1-1983 (R1992)
Angle between sides of thread is 60 degrees.
Thread taper, is 3⁄4 inch per foot.
All units are in inches.

ANSI/ASME B1.20.1-1983 (R2006)
All Dimensions Given in inches

Nominal Pipe Size	Wrench Makeup Length for Internal Thread		Vanish Thread, (3.47 thds.), V	Overall Length External Thread, L4	Nominal Perfect External Threads^a		Height of Thread, h	Basic Minor Dia. at Small End of Pipe,^b K₀
Nominal Pipe Size	Length,c L₃	Dia., E₃	Vanish Thread, (3.47 thds.), V	Overall Length External Thread, L4	Length, L₅	Dia., E₅	Height of Thread, h	Basic Minor Dia. at Small End of Pipe,^b K₀
1⁄16	0.1111	0.26424	0.1285	0.3896	0.1870	0.28287	0.02963	0.2416
1⁄8	0.1111	0.35656	0.1285	0.3924	0.1898	0.37537	0.02963	0.3339
1⁄4	0.1667	0.46697	0.1928	0.5946	0.2907	0.49556	0.04444	0.4329
3⁄8	0.1667	0.60160	0.1928	0.6006	0.2967	0.63056	0.04444	0.5676
1⁄2	0.2143	0.74504	0.2478	0.7815	0.3909	0.78286	0.05714	0.7013
3⁄4	0.2143	0.95429	0.2478	0.7935	0.4029	0.99286	0.05714	0.9105
1	0.2609	1.19733	0.3017	0.9845	0.5089	1.24543	0.06957	1.1441
11⁄4	0.2609	1.54083	0.3017	1.0085	0.5329	1.59043	0.06957	1.4876
11⁄2	0.2609	1.77978	0.3017	1.0252	0.5496	1.83043	0.06957	1.7265
2	0.2609	2.25272	0.3017	1.0582	0.5826	2.30543	0.06957	2.1995
2-1⁄2	0.2500d	2.70391	0.4337	1.5712	0.8875	2.77500	0.100000	2.6195
3	0.2500d	3.32500	0.4337	1.6337	0.9500	3.40000	0.100000	3.2406
3-1⁄2	0.2500	3.82188	0.4337	1.6837	1.0000	3.90000	0.100000	3.7375
4	0.2500	4.31875	0.4337	1.7337	1.0500	4.40000	0.100000	4.2344
5	0.2500	5.37511	0.4337	1.8400	1.1563	5.46300	0.100000	5.2907
6	0.2500	6.43047	0.4337	1.9462	1.2625	6.52500	0.100000	6.3461
8	0.2500	8.41797	0.4337	2.1462	1.4625	8.52500	0.100000	8.3336
10	0.2500	10.52969	0.4337	2.3587	1.6750	10.65000	0.100000	10.4453
12	0.2500	12.51719	0.4337	2.5587	1.8750	12.65000	0.100000	12.4328
14 OD	0.2500	13.75938	0.4337	2.6837	2.0000	13.90000	0.100000	13.6750
16 OD	0.2500	15.74688	0.4337	2.8837	2.2000	15.90000	0.100000	15.6625
18 OD	0.2500	17.73438	0.4337	3.0837	2.4000	17.90000	0.100000	17.6500
20 OD	0.2500	19.72188	0.4337	3.2837	2.6000	19.90000	0.100000	19.6375
24 OD	0.2500	23.69688	0.4337	3.6837	3.0000	23.90000	0.100000	23.6125

^aThe length L5 from the end of the pipe determines the plane beyond which the thread form is imperfect at the crest. The next two 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.
^b Given as information for use in selecting tap drills.
^cThree threads for 2-inch size and smaller; two threads for larger sizes.
^d 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 21⁄2 in., 2.69609 and size 3 in., 3.31719.

The basic dimensions 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.