Steel Pipe Schedule Chart (Sch 40 & 80)

Pipe is sized by NPS and schedule, not by its actual size. The outside diameter is fixed for a given NPS, and the schedule sets the wall thickness — a higher schedule means a thicker wall and a smaller bore. For example, NPS 2 pipe is 60.3 mm OD; a Sch 40 wall of 3.91 mm leaves a 52.5 mm bore, while Sch 80 thickens the wall to 5.54 mm and narrows the bore to 49.2 mm.

Rows

Columns

Basis

ASME B36.10M

Reviewed

June 1, 2026

Three numbers describe a pipe: the NPS (nominal pipe size — a label, not a measurement), the OD (outside diameter, fixed for each NPS so fittings interchange), and the ID (inside diameter, or bore). The schedule is the wall-thickness class: a higher schedule number means a thicker wall and therefore a smaller bore for the same OD. Schedule 40 is the original "standard" weight and Schedule 80 the old "extra strong." Note that pipe is not tube — tube is sized by its actual OD and wall, whereas pipe carries a nominal label whose OD only matches the NPS at sizes 14 and above.

Steel pipe dimensions by NPS and schedule (ID = OD − 2 × wall).

NPS

OD (mm)

OD (in)

Sch 40 wall (mm)

Sch 40 ID (mm)

Sch 80 wall (mm)

Sch 80 ID (mm)

1/8

10.3

0.405

1.73

6.84

2.41

5.48

1/4

13.7

0.540

2.24

9.22

3.02

7.66

3/8

17.1

0.675

2.31

12.48

3.20

10.70

1/2

21.3

0.840

2.77

15.76

3.73

13.84

3/4

26.7

1.050

2.87

20.96

3.91

18.88

33.4

1.315

3.38

26.64

4.55

24.30

1-1/4

42.2

1.660

3.56

35.08

4.85

32.50

1-1/2

48.3

1.900

3.68

40.94

5.08

38.14

60.3

2.375

3.91

52.48

5.54

49.22

2-1/2

73.0

2.875

5.16

62.68

7.01

58.98

88.9

3.500

5.49

77.92

7.62

73.66

114.3

4.500

6.02

102.26

8.56

97.18

168.3

6.625

7.11

154.08

10.97

146.36

219.1

8.625

8.18

202.74

12.70

193.70

273.1

10.750

9.27

254.56

12.70

247.70

323.9

12.750

10.31

303.28

12.70

298.50