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Pipe NPS Schedule 40 and Schedule 80 Dimensions and Weight Chart

Nominal pipe size is a label, not a measurement, so a buyer needs the outside diameter and schedule wall to be sure what is being ordered. This chart gives NPS, DN, outside diameter and the common Schedule 40 and 80 walls with a calculated steel weight.

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NPS (inch)DN (mm)OD (inch)Sch 40 wall (inch)Sch 80 wall (inch)OD (mm)Sch 40 wall (mm)Sch 80 wall (mm)Sch 40 kg/m (steel)Sch 80 kg/m (steel)
1/2
15
0.84
0.109
0.147
21.336
2.7686
3.7338
1.2677
1.6207
3/4
20
1.05
0.113
0.154
26.67
2.8702
3.9116
1.6845
2.1953
1
25
1.315
0.133
0.179
33.401
3.3782
4.5466
2.5011
3.2351
1-1/4
32
1.66
0.14
0.191
42.164
3.556
4.8514
3.3856
4.4639
1-1/2
40
1.9
0.145
0.2
48.26
3.683
5.08
4.0486
5.4093
2
50
2.375
0.154
0.218
60.325
3.9116
5.5372
5.4416
7.4811
2-1/2
65
2.875
0.203
0.276
73.025
5.1562
7.0104
8.6296
11.4124
3
80
3.5
0.216
0.3
88.9
5.4864
7.62
11.2854
15.2733
4
100
4.5
0.237
0.337
114.3
6.0198
8.5598
16.074
22.3201
6
150
6.625
0.28
0.432
168.275
7.112
10.9728
28.2651
42.5643
8
200
8.625
0.322
0.5
219.075
8.1788
12.7
42.5355
64.6329
10
250
10.75
0.365
0.594
273.05
9.271
15.0876
60.3059
95.9775
12
300
12.75
0.406
0.688
323.85
10.3124
17.4752
79.7338
132.0287

Outside diameters and nominal wall thicknesses follow ASME B36.10M for carbon steel pipe. Weight is calculated for plain-end carbon steel at 7.85 g/cm3 using kg/m = 0.02466 x t x (OD - t) with t and OD in mm. Published catalogue weights differ slightly and mill under-tolerance is not applied. Stainless steel is about 2 percent heavier.

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How to use the chart

Find the NPS or the DN you were quoted and read across to the outside diameter and wall thickness for the schedule on the drawing. Use the weight column to estimate freight, support loads and raw material cost. Search by DN when a European or Asian supplier quotes metric. Export to Excel to build a bill of material or a take-off sheet. Always confirm the final wall against the purchase specification since some lines call for XS, XXS or intermediate schedules not shown here.

Standards and method

ASME B36.10M defines dimensions of welded and seamless wrought steel pipe, and B36.19M covers stainless. Outside diameter stays the same across schedules for a given NPS, and only the wall changes, so the bore shrinks as the schedule rises. DN is the metric nominal size in millimetres and is roughly 25 times the NPS in inches, rounded to the preferred series. Weight per metre follows from the annular area multiplied by steel density.

  • NPS 2 is 60.3 mm outside diameter, not 50.8 mm
  • Schedule sets wall for each NPS, not a fixed thickness
  • Bore equals OD minus two walls
  • Tolerance on wall is typically minus 12.5 percent for seamless pipe

Common mistakes

Treating NPS as the outside diameter for sizes below 14 is the classic error. Another is assuming Schedule 40 and Standard weight are the same at all sizes: they match up to NPS 10 and then differ. Ordering by weight without allowing for the wall tolerance can also leave a shipment under its quoted tonnage. Finally, tube is specified by actual outside diameter and gauge, so do not mix pipe and tube tables in the same BOM.

Frequently Asked Questions

Is NPS 2 pipe really 2 inches across?

No. NPS 2 has an outside diameter of 2.375 inch (60.3 mm). For sizes up to NPS 12 the nominal size is only a label, and the bore depends on the schedule wall.

How is the weight per metre calculated?

Weight in kg per metre is 0.02466 multiplied by the wall in mm and by the outside diameter minus the wall, in mm. It assumes plain-end carbon steel at 7.85 g/cm3 and ignores coatings, threads and tolerances.

What is the difference between pipe and tube?

Pipe is sized by nominal size and schedule and is mainly for conveying fluids. Tube is sized by actual outside diameter and wall thickness or gauge and is used where tighter dimensional control matters.

Does the chart cover stainless pipe?

Outside diameters match, and the common Schedule 10S, 40S and 80S walls equal Schedule 40 and 80 for most small sizes. Stainless weighs about 2 percent more than carbon steel, so check the specification and ASME B36.19M for exact values.

If your pipe and fitting items live in the ERP with free text sizes, we can help standardise the size attributes so purchasing and costing read the same data.

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