American taper pipe thread (NPT)

EQUIVALENT: ANSI B1.20.1 · size designation NPS (nominal pipe size, inch)
SCOPE
UNITS: Dimensions mm (standard in inches; inch values for the selected size)

The CSV uses semicolons as separators. The link carries the selected size.

SIZE

Size	nthreads/in	Ppitch	Dpipe Ø	E0small end	L1hand-tight	E1	L2effective thread	E2	L4overall
1/16" NPT	27	0.941	7.95	6.90	4.06	7.14	6.63	7.30	9.90
1/8" NPT	27	0.941	10.29	9.23	4.10	9.49	6.70	9.65	9.97
1/4" NPT	18	1.411	13.72	12.13	5.79	12.49	10.21	12.76	15.10
3/8" NPT	18	1.411	17.14	15.54	6.10	15.93	10.36	16.19	15.26
1/2" NPT	14	1.814	21.34	19.26	8.13	19.77	13.56	20.11	19.85
3/4" NPT	14	1.814	26.67	24.58	8.61	25.12	13.86	25.45	20.16
1" NPT	11½	2.209	33.40	30.83	10.16	31.46	17.34	31.91	25.01
1 1/4" NPT	11½	2.209	42.16	39.55	10.67	40.22	17.95	40.67	25.62
1 1/2" NPT	11½	2.209	48.26	45.62	10.67	46.29	18.38	46.77	26.04
2" NPT	11½	2.209	60.33	57.63	11.07	58.33	19.21	58.83	26.88
2 1/2" NPT	8	3.175	73.03	69.08	17.32	70.16	28.89	70.88	39.91
3" NPT	8	3.175	88.90	84.85	19.46	86.07	30.48	86.76	41.50
3 1/2" NPT	8	3.175	101.60	97.47	20.85	98.78	31.75	99.46	42.77
4" NPT	8	3.175	114.30	110.09	21.44	111.43	33.02	112.16	44.04
5" NPT	8	3.175	141.30	136.93	23.80	138.41	35.72	139.16	46.74
6" NPT	8	3.175	168.28	163.73	24.33	165.25	38.42	166.13	49.43
8" NPT	8	3.175	219.07	214.21	27.00	215.90	43.50	216.93	54.51
10" NPT	8	3.175	273.05	267.85	30.73	269.77	48.90	270.91	59.91
12" NPT	8	3.175	323.85	318.33	34.54	320.49	53.98	321.71	64.99
14" NPT	8	3.175	355.60	349.88	39.67	352.37	57.15	353.46	68.17
16" NPT	8	3.175	406.40	400.37	46.02	403.24	62.23	404.26	73.25
18" NPT	8	3.175	457.20	450.85	50.80	454.02	67.31	455.06	78.33
20" NPT	8	3.175	508.00	501.33	53.98	504.71	72.39	505.86	83.41
24" NPT	8	3.175	609.60	602.30	60.33	606.07	82.55	607.46	93.57

Notes

This table has been compiled by Emsal from the relevant standards. For the full text of the standard, refer to ASME.
The thread seals: both internal and external threads are tapered (1:16 on diameter); a thread sealant (PTFE tape, liquid sealant) is applied. The profile is 60°.
NPT and ISO 7-1 (R / Rp) are not interchangeable: the profile angle (60° / 55°) and, in most sizes, the threads per inch differ. State the thread type clearly when ordering valves.
L1 (hand-tight engagement): the length of thread entering the body when the pipe is hand-tight; about 3 more turns are made with a wrench. L2 is the effective (full) thread length, L4 the overall thread length including vanish threads.
The size designation is the nominal pipe size (NPS); it is not the major diameter of the thread (1" NPT → pipe Ø33.40 mm).
Accuracy and currency are not guaranteed; use the current edition of the standard for design and purchasing decisions. How the library is compiled →

Dimension letters

D	Pipe outside diameter	L1	Hand-tight engagement length
E0	Pitch diameter at small end	L2	Effective thread length
E1	Pitch diameter at L1 plane	L4	Overall thread length
E2	Pitch diameter at L2 plane	n · P	Threads/in · pitch

Joint type and P&ID symbol

With NPT both the male and female threads are tapered. Sealing is made on the thread with tape or compound (the NPTF "dryseal" thread needs no sealant).

female partmale part, pipegasket / sealing tapethread

Wrap PTFE tape on the male thread or apply compound.
Screw in by hand and tighten with a wrench.
Do not combine with BSP (R, G) parts.

Used on ASME and API valves and equipment and in plants of American origin. Although it looks the same size as BSP, the thread angle is 60° and the pitch differs; mixing them causes leaks.

P&ID: Threaded jointTwo short thin lines perpendicular to the pipeline. Symbol library →

Not to scale; proportions are indicative.

Our products with this thread standard

Ball valvesThreaded connection · NPT (export)

Check valvesThreaded models

StrainersThreaded Y-type