Pipe Threading Standards

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Pipe Threading Acronyms

NPS: Nominal Pipe Size (Not the pipe ID or OD)
NPT: National Pipe Thread (tapered) is a U.S. standard for tapered threads
FPT, or FNPT, or NPT(F): Female Pipe Thread (interchangeable with NPT)
FIP: Female Iron Pipe (interchangeable with NPT)
MPT, MNPT or NPT(M): Male Pipe Thread (interchangeable with NPT)
MIP: Male Iron Pipe (interchangeable with NPT)
NPTF: National (American Dryseal)) Pipe Thread, Fuel, for leak-free seal without thread sealant
NPS: National (American) Pipe Straight (parallel thread instead of taper) uses a gasket or O-ring to seal.
NPSF: National (American) Pipe Straight (parallel thread instead of taper) Fuel
BSPT: British Standard Pipe Thread Tapered
BSPP: British Standard Pipe Thread Parallel
IPS: Iron Pipe Straight
IPT: Iron Pipe Thread
TPI: Threads Per Inch
WOG: Water Oil Gas
SCH: Schedule
UNF: Unified Fine Thread Series
NPT: Pipe Thread Sizes

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	0.037	0.940	0.16	4.32	0.281	0.261	7.05	0.288	0.390	0.313	7.95
¹⁄₈	27	0.037	0.940	0.161	4.36	0.374	0.264	7.13	0.380	0.392	0.405	10.29	0.339	8.611
¹⁄₄	18	00.056	1.411	0.227	4.1	0.492	0.402	7.23	0.503	0.595	0.54	13.72	⁷⁄₁₆	11.11
³⁄₈	18	00.056	1.411	0.24	4.32	0.627	0.408	7.34	0.638	0.601	0.675	17.15	³⁷⁄₆₄	14.69
¹⁄₂	14	00.071	1.814	0.32	4.48	0.778	0.534	7.47	0.792	0.782	0.84	21.34	²³⁄₃₂	18.257
³⁄₄	14	00.071	1.814	0.339	4.75	0.989	0.546	7.64	1.002	0.794	1.05	26.67	⁵⁹⁄₆₄	23.416
1	11 ¹⁄₂	0.087	2.208	0.4	4.6	1.24	0.683	7.85	1.256	0.985	1.315	33.40	1 ⁵⁄₃₂	29.37
1 ¹⁄₄	11 ¹⁄₂	0.087	2.208	0.42	4.83	1.58	0.707	8.13	1.601	1.009	1.66	42.16	1 ¹⁄₂	38.1
1 ¹⁄₂	11 ¹⁄₂	00.087	2.208	0.42	4.83	1.822	0.724	8.32	1.841	1.025	1.9	48.26	1 ⁴⁷⁄₆₄	44.05
2	11 ¹⁄₂	0.087	2.208	0.436	5.01	2.300	0.757	8.7	2.316	1.058	2.375	60.33	2 ⁷⁄₃₂	56.36
2 ¹⁄₂	8	0.125	3.175	0.682	5.46	2.762	1.138	9.1	2.791	1.571	2.875	73.03	2 ⁵⁄₈	66.68
3	8	0.125	3.175	0.766	6.13	3.39	1.20	9.6	3.416	1.634	3.5	88.9	3 ¹⁄₄	82.55
3 ¹⁄₂	8	0.125	3.175	0.821	6.57	3.89	1.25	10	3.916	1.684	4	101.6	3 ³⁄₄	95.25
4	8	0.125	3.175	0.844	6.75	4.39	1.3	10.4	4.416	1.734	4.5	114.3	4 ¹⁄₄	107.95
4 ¹⁄₂	8	0.125	3.175								5	127	4 ³⁄₄	120.65
5	8	0.125	3.175	0.937	7.5	5.449	1.406	11.25	5.479	1.84	5.563	141.30	5 ⁹⁄₃₂	134.14
6	8	0.125	3.175	0.958	7.66	6.506	1.513	12.1	6.541	1.946	6.625	168.28	6 ¹¹⁄₃₂	161.13
8	8	0.125	3.175	1.063	8.5	8.500	1.713	13.7	8.541	2.146	8.625	219.06
10	8	0.125	3.175	1.21	9.68	10.62	1.93	15.4	10.666	2.359	10.75	273.05
12	8	0.125	3.175	1.36	10.88	12.62	2.13	17	12.666	2.559	12.75	323.85
14	8	0.125	3.175	1.562	12.5	13.87	2.25	18	13.916	2.684	14	355.6
16	8	0.125	3.175	1.812	14.5	15.88	2.45	19.6	15.916	2.884	16	406.4
18	8	0.125	3.175	2	16	17.88	2.65	21.2	17.916	3.084	18	457.2
20	8	0.125	3.175	2.125	17	19.87	2.85	22.8	19.916	3.284	20	508
24	8	0.125	3.175	2.375	19	23.86	3.25	26	23.916	3.684	24	609.6

Information is based on Wikipedia article, National pipe thread and is for reference only and should be verified by related pipe thread standards. Number of decimals expressed not necessarily indicative of manufacturing tolerances.

The information may be used but with no warranty or liability. These pipe thread standard definitions are believed to be correct but should always be double-checked with alternative sources. Strictly adhere to and follow all applicable national and local regulations and practices.