National pipe thread

American National Standard Pipe Thread standards, often called national pipe thread standards for short, are U.S. national technical standards for screw threads used on threaded pipes and pipe fittings. They include both tapered and straight thread series for various purposes including rigidity, pressure-tight sealing, or both.^[1] The various types are each named with a symbol and a full name; examples of the symbols include NPT, NPS, NPTF, NPSC, and others.

MIP is an acronym for male iron pipe, and FIP is an acronym for female iron pipe.^[2]

Outside the United States, some US pipe threads are found, as well as many British Standard Pipe threads and ISO 7-1, 7-2, 228-1, and 228-2 threads.

The various types are each named with a symbol and a full name, as follows:^[3]

Symbol^[3]	Shorthand expansion	Full name^[3]	Comment^[3]
NPT	national pipe taper	American National Standard Taper Pipe Thread	Tapered for sealing, often without any thread sealant; for connections in nearly every type of service
NPS	national pipe straight	American National Standard Straight Pipe Thread	For rigidity; sealable only with sealant; sometimes male straight enclosed by female tapered for low-pressure sealing
NPSC	national pipe straight–coupling	American National Standard Straight Pipe Thread for Couplings	For general couplings
NPSF	national pipe straight–fuel	Dryseal USA (American) Standard Fuel Internal Straight Pipe Thread	Internal only, straight
NPSH	national pipe straight–hose	American National Standard Straight Pipe Thread for Hose Couplings	For hose couplings
NPSI	national pipe straight–intermediate	Dryseal USA (American) Standard Intermediate Internal Straight Pipe Thread	Similar to NPSF but slightly larger; internal only, straight
NPSL	national pipe straight–locknut	American National Standard Straight Pipe Thread for Loose-fitting Mechanical Joints with Locknuts	For use with locknuts
NPSM	national pipe straight–mechanical	American National Standard Straight Pipe Thread for Free-fitting Mechanical Joints	For various rigid mechanical uses
NPTF	national pipe taper–fuel	Dryseal USA (American) Standard Taper Pipe Thread	For dryseal connections in nearly every type of service, especially fuel connections
NPTR	national pipe taper–railing	American National Standard Taper Pipe Thread for Railing Joints	For railings
PTF-SAE SHORT	pipe taper, fuel, SAE, short	Dryseal SAE Short Taper Pipe Thread	Named after SAE International; similar to NPTF but one turn shorter

Standard sizes

American Society of Mechanical Engineers National Pipe Thread Taper (NPT) www.bd-pipefitting.com

Nominal pipe size	Thread density	Thread pitch		Hand-tight engagement			Effective thread			Overall length	Actual outside diameter, OD		Tap drill
Nominal pipe size	Thread density	Thread pitch		Length	Turns	Diameter	Length	Turns	Diameter	Overall length	Actual outside diameter, OD		Tap drill
inch	inch⁻¹	inch	mm	inch		inch	inch		inch	inch	inch	mm	inch	mm
¹⁄₁₆	27	0.03703704	0.9407	0.1600	4.32	0.28118	0.2611	7.05	0.2875	0.3896	0.313	7.950
¹⁄₈	27	0.03703704	0.9407	0.1615	4.36	0.37360	0.2639	7.13	0.38000	0.3924	0.405	10.287	0.339	8.6106
¹⁄₄	18	0.05555555	1.4111	0.2278	4.10	0.49163	0.4018	7.23	0.50250	0.5946	0.540	13.716	⁷⁄₁₆	11.113
³⁄₈	18	0.05555555	1.4111	0.2400	4.32	0.62701	0.4078	7.34	0.63750	0.6006	0.675	17.145	³⁷⁄₆₄	14.684
¹⁄₂	14	0.07142857	1.8143	0.3200	4.48	0.77843	0.5337	7.47	0.79178	0.7815	0.840	21.3360	²³⁄₃₂	18.2563
³⁄₄	14	0.07142857	1.8143	0.3390	4.75	0.98887	0.5457	7.64	1.00178	0.7935	1.050	26.6700	⁵⁹⁄₆₄	23.4156
1	11 ¹⁄₂	0.08695652	2.2087	0.4000	4.60	1.23863	0.6828	7.85	1.25631	0.9845	1.315	33.4010	1 ⁵⁄₃₂	29.3688
1 ¹⁄₄	11 ¹⁄₂	0.08695652	2.2087	0.4200	4.83	1.58338	0.7068	8.13	1.60131	1.0085	1.660	42.1640	1 ¹⁄₂	38.1000
1 ¹⁄₂	11 ¹⁄₂	0.08695652	2.2087	0.4200	4.83	1.82234	0.7235	8.32	1.84131	1.0252	1.900	48.2600	1 ⁴⁷⁄₆₄	44.0531
2	11 ¹⁄₂	0.08695652	2.2087	0.4360	5.01	2.29627	0.7565	8.70	2.31630	1.0582	2.375	60.3250	2 ⁷⁄₃₂	56.3563
2 ¹⁄₂	8	0.12500000	3.1750	0.6820	5.46	2.76216	1.1375	9.10	2.79063	1.5712	2.875	73.0250	2 ⁵⁄₈	66.6750
3	8	0.12500000	3.1750	0.7660	6.13	3.38850	1.2000	9.60	3.41563	1.6337	3.500	88.9000	3 ¹⁄₄	82.5500
3 ¹⁄₂	8	0.12500000	3.1750	0.8210	6.57	3.88881	1.2500	10.00	3.91563	1.6837	4.000	101.6000	3 ³⁄₄	95.2500
4	8	0.12500000	3.1750	0.8440	6.75	4.38713	1.3000	10.40	4.41563	1.7337	4.500	114.3000	4 ¹⁄₄	107.9500
4 ¹⁄₂	8	0.12500000	3.1750								5.000	127.0000	4 ³⁄₄	120.6500
5	8	0.12500000	3.1750	0.9370	7.50	5.44929	1.4063	11.25	5.47863	1.8400	5.563	141.3002	5 ⁹⁄₃₂	134.1438
6	8	0.12500000	3.1750	0.9580	7.66	6.50597	1.5125	12.10	6.54063	1.9462	6.625	168.2750	6 ¹¹⁄₃₂	161.1313
8	8	0.12500000	3.1750	1.0630	8.50	8.50003	1.7125	13.70	8.54063	2.1462	8.625	219.0750
10	8	0.12500000	3.1750	1.2100	9.68	10.62094	1.9250	15.40	10.66563	2.3587	10.750	273.0500
12	8	0.12500000	3.1750	1.3600	10.88	12.61781	2.1250	17.00	12.66563	2.5587	12.750	323.8500
14	8	0.12500000	3.1750	1.5620	12.50	13.87263	2.2500	18.00	13.91563	2.6837	14.000	355.6000
16	8	0.12500000	3.1750	1.8120	14.50	15.87575	2.4500	19.60	15.91563	2.8837	16.000	406.4000
18	8	0.12500000	3.1750	2.0000	16.00	17.87500	2.6500	21.20	17.91563	3.0837	18.000	457.2000
20	8	0.12500000	3.1750	2.1250	17.00	19.87031	2.8500	22.80	19.91563	3.2837	20.000	508.0000
24	8	0.12500000	3.1750	2.3750	19.00	23.86094	3.2500	26.00	23.91563	3.6837	24.000	609.6000

Hand-tight and effective thread engagement length
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Bangdong Knowlege of NPT Thread

National pipe thread

Standard sizes