NPS (Nominal Pipe Size) Guide: Dimensions & Specifications

A comprehensive guide to Nominal Pipe Size (NPS) and DN (Diameter Nominal) standards, showing the relationship between nominal sizes, outside diameters, and various international piping standards including ISO 6708, DIN EN 10220, DIN EN 10255, and ASME specifications.

Nominal Pipe Size (NPS)	DN (mm)	Outside Diameter (Inch)	ISO 6708 (mm)	DIN EN 10220 (mm)	DIN EN 10255 (mm)	ASME (mm)
10	10	3/8	17.2	-	-	-
15	15	1/2	21.3	20.0	21.3	21.3
20	20	3/4	26.9	25.0	26.9	26.7
25	25	1	33.7	30.0	33.7	33.4
32	32	1 1/4	42.4	38.0	42.4	42.2
40	40	1 1/2	48.3	44.5	48.3	48.3
50	50	2	60.3	57.0	60.3	60.3
-	65	2 1/2	-	-	73.0	73.0
-	65	-	76.1	76.1	76.1	-
80	80	3	88.9	88.9	88.9	88.9
-	80	3 1/2	-	-	101.6	101.6
100	100	4	114.3	108	114.3	114.3
125	125	-	139.7	133	139.7	-
-	125	5	-	-	141.3	141.3
150	150	6	168.3	159	168.3	168.3
200	200	8	219.1	216	219.1	219.1
250	250	10	273.0	267	273.0	273.0
300	300	12	323.9	318	323.9	323.8
350	350	14	355.6	368	355.6	355.6
400	400	16	406.4	419	406.4	406.4
450	450	18	457	470	457	457
500	500	20	508	521	508	508
600	600	24	610	622	610	610
700	700	28	711	720	711	711
800	800	32	813	820	813	813
900	900	36	914	920	914	914
1000	1000	40	1016	1020	1016	1016
1200	1200	48	1220	1219	1219	-