Stainless Steel Tube & Pipe Sizes and Dimensions

There are several common methods for describing pipe and tube dimension used in tubular piping system, we should calculate exact sizes without confusion.

Nominal Pipe Size

The North American ANSI system is widely applied in pipe system, Nominal Pipe Size (NPS) is defined standard sizes for pipes used for different pressures and temperatures, the outside diameter is used in inches, NPS and OD values are not always equal, from NPS ⅛ to 12 inch, the NPS and OD values are different, over 14 inch, the NPS and OD values are equal, the size is actual dimensions, not nominal.

NB

NB (Nominal Bore) is also another method to refer pipe sizes and dimensions, it is the same value between NB and NPS.

Pipe Schedule

Wall thickness referred to as the Schedule (Sch.), nowadays, there are large selection of wall thicknesses to meet all applications under different pressure, standard weight (STD), extra-strong (XS), and double extra-strong (XXS) is three main number for thickness, 5S and 10S are thinner wall thickness for stainless steel pipe.

DN Size

The European ISO system is also OD based, Diameter Nominal (DN) is also frequently referred to pipe dimensions, it provides almost the same OD as the ANSI system, but measured in millimeters, and with a lot more choices for different wall thickness.

Nominal Pipe Size Chart, Diameter Nominal pipe dimension and pipe Schedule base on ANSI B36.19 (Stainless Steel Pipe).& B36.10.

Nominal Size OD Wall Thickness, SCH
NPS hN mm 5S 10S 10 20 30 40S STh 40 60 80S XS 80 100 120 140 160 XXS
1∕8 6 10.3 1.24 1.73 1.73 1.73 2.41 2.41 2.41
1∕4 8 13.7 1.65 2.24 2.24 2.24 3.02 3.02 3.02
3∕8 10 17.2 1.65 2.31 2.31 2.31 3.2 3.2 3.2
1∕2 15 21.3 1.65 2.11 2.77 2.77 2.77 3.73 3.73 3.73 4.78 7.47
3∕4 20 26.7 1.65 2.11 2.87 2.87 2.87 3.91 3.91 3.91 5.56 7.82
1 25 33.4 1.65 2.77 3.38 3.38 3.38 4.55 4.55 4.55 6.35 9.09
1 1∕4 32 42.2 1.65 2.77 3.56 3.56 3.56 4.85 4.85 4.85 6.35 9.7
1 1∕2 40 48.3 1.65 2.77 3.68 3.68 3.68 5.08 5.08 5.08 7.14 10.15
2 50 60.3 1.65 2.77 3.91 3.91 3.91 5.54 5.54 5.54 8.74 11.07
2 1∕2 65 73 2.11 3.05 5.16 5.16 5.16 7.01 7.01 7.01 9.53 14.02
3 80 88.9 2.11 3.05 5.49 5.49 5.49 7.62 7.62 7.62 11.13 15.24
3 1∕2 90 101.6 2.11 3.05 5.74 5.74 5.74 8.08 8.08 8.08
4 100 114.3 2.11 3.05 6.02 6.02 6.02 8.56 8.56 8.56 11.13 13.49 17.12
5 125 141.3 2.77 3.4 – – 6.55 6.55 6.55 9.53 9.53 9.53 12.7 15.88 19.05
6 150 168.3 2.77 3.4 7.11 7.11 7.11 10.97 10.97 10.97 14.27 18.26 21.95
8 200 219.1 2.77 3.76 6.35 7.04 8.18 8.18 8.18 10.31 12.7 12.7 12.7 15.09 18.26 20.62 23.01 22.23
10 250 273.1 3.4 4.19 6.35 7.8 9.27 9.27 9.27 12.7 12.7 12.7 15.09 18.26 21.44 25.4 28.58 25.4
12 300 323.9 3.96 4.57 6.35 8.38 9.53 9.53 10.31 14.27 12.7 12.7 17.48 21.44 25.4 28.58 33.32 25.4
14 350 355.6 3.96 4.78 6.35 7.92 9.53 9.53 11.13 15.09 12.7 19.05 23.83 27.79 31.75 35.71
16 400 406.4 4.19 4.78 6.35 7.92 9.53 9.53 12.7 16.66 12.7 21.44 26.19 30.96 36.53 40.49
18 450 457.2 4.19 4.78 6.35 7.92 11.13 9.53 14.27 19.05 12.7 23.83 29.36 34.93 39.67 45.24
20 500 508 4.78 5.54 6.35 9.53 12.7 9.53 15.09 20.62 12.7 26.19 32.54 38.1 44.45 50.01
22 550 558.8 4.78 5.54 6.35 9.53 12.7 9.53 22.23 12.7 28.58 34.93 41.28 47.63 53.98
24 600 609.6 5.54 6.35 6.35 9.53 14.27 9.53 17.48 24.61 12.7 30.96 38.89 46.02 52.37 59.54
26 650 660.4 7.92 12.7 9.53 12.7
28 700 711.2 7.92 12.7 15.88 9.53 12.7
30 750 762 6.35 7.92 7.92 12.7 15.88 9.53 12.7
32 800 812.8 7.92 12.7 15.88 17.48 9.53 17.48 12.7
34 850 863.6 7.92 12.7 15.88 17.48 9.53 17.48 12.7
36 900 914.4 7.92 12.7 15.88 19.05 9.53 19.05 12.7
38 950 965.2 9.53 12.7
40 1000 1016 9.53

From above table, we can see that

  • NPS and DN value are different, there have a corresponding value for outside diameter in millimeter.
  • From 1/8 inch to 12 inch (including) the value is nominal, not actual, for example, NPS 6 inch (DN150), pipe outside diameter should be 168.3 mm, not 152.4 mm.
  • From 14 inch, pipe OD should actual dimension, for example, NPS20 inch, the diameter should be 508 mm, it convert inch to mm by multiplying it with 25.4.
  • There are different Schedule number for choosing, from SCH5 – SCH160, for stainless steel pipe, there are SCH5S, SCH10S, SCH40S, SCH80.

Difference between pipe and tube dimension

Generally, NPS is a pipe sizes number, the diameter is expressed in inch, it has corresponding value in mm, and schedule number is for pipe thickness mentioned.

Tube sizes is expressed in inch or millimeter, it is actual value both outside diameter and wall thickness, tube is used in heating system, like cooler tubes, heat exchanger tubes and boiler tubes, and structural part.

tube pipe dimension difference

BWG

Birmingham Wire Gauge (BWG) also offers a wide range of different gauges for tube wall thickness, for example, BWG16, the wall thickness is 1.65 mm, the conversion in inch and mm as following: