External Pipe Thread Design, Specifications and NPT Pipe Thread Tolerances

Hardware ANSI Menu >

NPT, ANPT and NPTF thread data Table. Note that NPT 5" to 24" OD sizes are not included in the table.

NPT, ANPT and NPTF

NPTR

NPTG and NPTC

External Pipe NPT Thread Dimensional Data Table

Pipe Size	T.P.I	D
		O.D.	O.D. of Valve
		NPT ANPT NPTR NPTF	NPTG	NPTC
1/16	27	.313	-	-
1/8	27	.405	-	-
1/4	18	.540	-	-
3/8	18	.675	-	-
1/2	14	.840	.863	-
3/4	14	10.05	1.081	-
3/4-14NPTC-1		-	-	1.096
3/4-14NPTC-2		-	-	1.114
3/4-14NPTC-3		-	-	1.134
3/4-14NPTC-4		-	-	.159
1	11-1/2	1.315	1.346	-
1-1/2	11-1/2	1.660	-	-
1-1/2	11-1/2	1.900	-	-
2	11-1/2	2.375	-	-
2-1/2	8	2.875	-	-
3	8	3.500	-	-
* 3-1/2	8	4.000	-	-
* 4	8	4.500	-	-

* Does not include ANPT, NPTF, NPTG or NPTC.

Pipe Size	T.P.I	Pitch Dia. Small End Pipe
		Eo	Tolerance		E6	Tolerance
		NPT ANPT NPTF NPTG NPTC	Turns of Gage	Inches on Dia.	NPTR	Turns of Gage	Inches on Dia.
1/16	27	.2712	One Turn Large One Turn Small	± .0023	-	One Turn Large One Turn Small
1/8	27	.3635		± .0023	-
1/4	18	.4774		± .0035	-
3/8	18	.6120		± .0035	-
1/2	14	.7584		± .0045	.7718		+ .0000 - .0045
3/4	14	.9677		± .0045	.9811		+ .0000 - .0045
3/4-14NPTC-1		.9677		± .0045	-		+ .0000 - .0045
3/4-14NPTC-2		.9856		± .0045	-		+ .0000 - .0045
3/4-14NPTC-3		1.0057		± .0045	-		+ .0000 - .0045
3/4-14NPTC-4		1.0302		± .0045	-		+ .0000 - .0045
1	11-1/2	1.2136		± .0054	1.2299		+ .0000 - .0054
1-1/2	11-1/2	1.5571		± .0054	1.5734		+ .0000 - .0054
1-1/2	11-1/2	1.7961		± .0054	1.8124		+ .0000 - .0054
2	11-1/2	2.2690		± .0054	2.2853		+ .0000 - .0054
2-1/2	8	2.7195		± .0078	2.7508		+ .0000 - .0078
3	8	3.3406		± .0078	3.3719		+ .0000 - .0078
* 3-1/2	8	3.8375		± .0078	3.8688		+ .0000 - .0078
* 4	8	4.3344		± .0078	4.3656		+ .0000 - .0078

* Does not include ANPT, NPTF, NPTG or NPTC.

Pipe Size	T.P.I	Pitch Dia. Small End Pipe
		Eo	Tolerance
		NPT ANPT NPTR NPTF	NPTG at L1 + S Thrd	MNPTC at L1 + 8-1/2 Thrd
1/16	27	.2875	-	-
1/8	27	.3800	-	-
1/4	18	.5025	-	-
3/8	18	.6375	-	-
1/2	14	.7918	.8008	-
3/4	14	1.0018	1.0112	-
3/4-14NPTC-1		-	-	1.0268
3/4-14NPTC-2		-	-	1.0447
3/4-14NPTC-3		-	-	1.0648
3/4-14NPTC-4		-	-	1.0893
1	11-1/2	1.2563	1.2658	-
1-1/2	11-1/2	1.613	-	-
1-1/2	11-1/2	1.8413	-	-
2	11-1/2	2.3163	-	-
2-1/2	8	2.7906	-	-
3	8	3.4156	-	-
* 3-1/2	8	3.9156	-	-
* 4	8	4.4156	-	-

---

Length specification Table for NPT, ANPT, NPTF, NPTR, NPTG and NPTC pipe threads

Pipe Size	Threads Per. inch	Pitch	Handtight Engaged	Effective Thread Length
				NPT ANPT NPTF	NPTR	NPTG NPTC
1/16	27	.0370	.16	.2611	-	-
1/8	27	.0370	.180	.2639	-	-
1/4	18	.0556	.200	.4018	-	-
3/8	18	.0556	.240	.4078	-	-
1/2	14	.0714	.320	.5337	.320	.6771
3/4	14	.0714	.339	.5457	.332	.6964
3/4-14NPTC-1		.0714	.339	-	-	.9461
3/4-14NPTC-2		.0714	.339	-	-	.9461
3/4-14NPTC-3		.0714	.339	-	-	.9461
3/4-14NPTC-4		.0714	.339	-	-	.9461
1	11-1/2	0.870	.400	.6828	.422	.8348
1-1/2	11-1/2	0.870	.420	.7068	.446	-
1-1/2	11-1/2	0.870	.420	.7235	.463	-
2	11-1/2	0.870	.436	.7565	.496	-
2-1/2	8	.1250	.682	1.1375	.638	-
3	8	.1250	.766	1.2000	.700	-
* 3-1/2	8	.1250	.821	1.2500	.750	-
* 4	8	.1250	.844	1.3000	.800	-

 

---

Mechanical Tolerances for Taper Pipe Threads
Click on image below to enlarge