How to Describe Steel Pipe Dimensions

When ordering steel pipes, the necessary pipe dimensions are diameter, wall thickness and length. There are various methods to describe the diameter and wall thickness, here I will introduce you some commonly used type.

Steel Pipe Diameters

For the pipe diameter, there are mainly three ways to describe it.

NPS: NPS means Nominal Pipe Size, a North American standard set of pipe sizes for high or low pressure and temperature applications. The diameter is specified in inches, e.g. NPS 8 pipe means the diameter of the pipe is 8 inches. It is used more than the actual size of the pipe as a way of distinguishing and naming pipes. NPS is often mistakenly called national pipe size due to confusion with national pipe thread NPT.

DN: DN is the METRIC equivalent of NPS and is widely used in Europe and internationally. Its designations conform to the usage of the International Standard Organization (ISO). DN and NPS can be converted to each other. For example, DN40 = NPS 1 1/2, DN 100 = NPS 4.

OD: This means Outside Diameter of the pipe and is fixed for a given size. Pipe in OD is often described in mm, such as OD108mm. NPS is very loosely related to OD in inches, only for NPS 1/8 to NPS 12. For NPS 14 and larger, it is equal to the OD in inches.

The steel pipe diameter is avaliable in 1/8 inch to 48 inch (DN6 to DN1200).

Wall Thickness of Pipes

For the wall thickness, schedule and mm （millimeter） are are very popular units.

Pipe schedule is the term used to describe the thickness of a pipe. The outside diameter of a pipe is the same for all schedules in a given nominal pipe size. There are 14 commonly used schedule numbers: Sch5, Sch10, Sch20, Sch30, Sch STD, Sch40, Sch60, Sch XS, Sch80, Sch100, Sch120, Sch140, Sch160, and Sch XXS. The most popular schedule is Sch40.

The schedule number is defined as the approximate
value of the expression:

Schedule Number= 1000 P/S

• P = the internal working pressure, psig
• S = the allowable stress (psi) for the material of construction at the conditions of use.

Millimeter is intuitively reflect the thickness of pipe wall. It can be used with NPS, DN or OD.

Wall thickness range for steel pipe is Sch 5 to Sch XXS.

Pipe Length

The pipe length is usually expressed in inches, meter or millimeter. Such as L=6m. Pipe length is available in Single Random, Double Random or Cut Length.

Therefore, the description of pipe dimensions can be DN40 Sch 40 x 6m Pipe.

Steel Pipe Manufacturer

What’s more, materials are also important when ordering pipes. The common grades for stainless steel pipes are SS 304, SS316, for carbon steel pipes are API 5LB, A106, A105, A234 WPB.

C&N is China leading manufacturer for steel pipes, we supply stainless steel pipe, carbon steel pipe, duplex steel pipe, alloy steel pipe in customized dimensions.

Sch 40 Steel Pipe Dimension Chart

Nominal Size	Nominal Size	Outside Diameter	Outside Diameter	Wall Thickness	Wall Thickness	Weight
NPS	DN	Inches	MM	Inches	MM	KG/M
1/8	8	0.41	10.3	0.068	1.73	0.37
3/8	10	0.54	13.7	0.088	2.24	0.63
1/4	12	0.68	17.1	0.091	2.31	0.84
1/2	15	0.84	21.3	0.109	2.77	1.27
3/4	20	1.05	26.7	0.113	2.87	1.69
1	25	1.32	33.4	0.133	3.38	2.5
1 1/4	32	1.66	42.2	0.14	3.56	3.39
1 1/2	40	1.9	48.3	0.145	3.68	4.05
2	50	2.375	60.3	0.154	3.91	5.44
2 1/2	65	2.875	73	0.203	5.16	8.63
3	80	3.5	88.9	0.216	5.49	11.29
3 1/2		4	101.6	0.226	5.74	13.57
4	100	4.5	114.3	0.237	6.02	16.07
5	125	5.563	141.3	0.258	6.55	21.77
6	150	6.625	168.3	0.28	7.11	28.26
8	200	8.625	219.1	0.322	8.18	42.55
10	250	10.75	273	0.365	9.27	60.31
12	300	12.75	323.8	0.406	10.31	79.73
14	350	14	355.6	0.437	11.13	94.55
16	400	16	406.4	0.5	12.7	123.3
18	450	18	457	0.562	14.27	155.8
20	500	20	508	0.594	15.09	183.42
24	600	24	610	0.688	17.48	255.41
32	800	32	813	0.688	17.48	342.91