NPT Thread Data Chart

						Basic Dimensions US Standard Taper Pipe Thread, NPT Extracted, in part, from USA Standard Pipe Threads (Except Dryseal) (ANSI B2.1—1968) with permission from the publisher, The American Society of Mechanical Engineers.

Nominal Pipe Size	Outside Diameter of Pipe D	Threads Per Inch n	Pitch of Thread P	Standard Pipe Thread, NPT					Short Plumbing (Hospital) Thread		Suggested Twist Drill Diameters for Drilled Hole Sizes For Pipe Threads 1 American Standard Twist Drill Sizes
				Hand tight Engagement Length L1		Effective Thread, External Length L1		Overall Length External Thread	Overall Length External Thread L4
				Inch	Threads	Inch	Threads	L4	Inch	Threads	Taper Thread	Straight Thread
1/8	0.405	27	0.03704	0.1615	4.36	0.2639	7.12	0.3924	10.260	17	0.332'	11/32 0.344'
1/4	0.540	18	0.05556	0.2278	4.10	0.4018	7.23	0.5946	0.400	7	7/16 0.438'	7/16 0.438'
3/8	0.675	18	0.05556	0.240	4.32	0.4078	7.34	0.6006	0.410	7	9/16 0.562'	37/64 0.578'
1/2	0.840	14	0.07143	0.320	4.48	0.5337	7.47	0.7815	0.530	7	45/64 0.703'	23/32 0.719'
3/4	1.050	14	0.07143	0.339	4.75	0.5457	7.64	0.7935	0.550	7-1/2	29/32 0.906'	59/64 0.922'
1	1.315	11-1/2	0.08696	0.400	4.60	0.6828	7.85	0.9845	0.680	7-1/2	1-9/64 1.141'	1-5/32 1.156'
1-1/4	1.660	11-1/2	0.08696	0.420	4.83	0.7068	8.13	1.0085	0.710	8	1-31/64 1.484	1-1/2 1.500
1-1/2	1.900	11-1/2	0.08696	0.420	4.83	0.7235	8.32	1.0252	0.720	8	1-47/64 1.734	1-3/4 1.750
2	2.375	11-1/2	0.08696	0.436	5.01	0.7565	8.70	1.0582	0.760	8-1/2	2-13/64 2.203	2-7/32 2.219
2-1/2	2.875	8	0.12500	0.682	5.46	1.1375	9.10	1.5712			2-5/8 2.625	2-21/32 2.656
3	3.500	8	0.12500	0.766	6.13	1.2000	9.60	1.6337
3-1/2	4.00	8	0.12500	0.821	6.57	1.2500	10.00	1.6837
4	4.500	8	0.12500	0.844	6.75	1.3000	10.4	1.7337
5	5.563	8	0.12500	0.937	7.50	1.4063	11.25	1.8400
6	6.625	8	0.12500	0.958	7.66	1.5125	12.10	1.9462
8	8.625	8	0.12500	1.063	8.50	1.7125	13.70	2.1462

Basic Dimensions

US Standard Taper Pipe Thread, NPT