What is a Pipe Schedule?
Pipes are designed to carry fluid; therefore their internal diameter is their critical dimension. This critical dimension is referred to as the nominal bore, abbreviated as NB. Obviously, for pipes containing pressurized fluids the wall thickness, and by implication the pipe's strength, is important. Wall thickness is expressed in "schedules", referred to as pipe schedules.
 
The wall thickness associated with a particular schedule depends on the pipe size as can be seen from the charts below for some of the more common sized carbon steel pipes encountered.
 
Abbreviations used: NB - nominal bore, STD - Standard, EH - Extra Heavy, DBL EH - Double Extra Heavy.
 

 2"NB

OD = 2.375 inch (60.32 mm)

Schedule

5

10

20

30

40
STD

60

80
EH

100

120

140

160

DBL EH

ID (ins)

2.245

2.157

---

---

2.067

---

1.939

---

---

---

1.689

1.503

ID (mm)

57.02

54.79

---

---

52.5

---

49.25

---

---

---

42.9

38.18


 

 3" NB

OD = 3.5 inch (88.9 mm)

Schedule

5

10

20

30

40
STD

60

80
EH

100

120

140

160

DBL
EH

ID (ins)

3.334

3.260

---

---

3.068

---

2.900

---

---

---

2.624

2.300

ID (mm)

84.68

82.8

---

---

77.93

---

73.66

---

---

---

66.65

58.42


 

 4" NB

OD = 4.5 inch (114.3 mm)

Schedule

5

10

20

30

40
STD

60

80
EH

100

120

140

160

DBL EH

ID (ins)

4.334

4.260

---

---

4.026

---

3.826

---

3.624

---

3.438

3.152

ID (mm)

110.08

108.2

---

---

102.26

---

97.18

---

92.05

---

87.33

80.06


 

 6" NB

OD = 6.625 inch (168.275 mm)

Schedule

5

10

20

30

40
STD

60

80
EH

100

120

140

160

DBL EH

ID (ins)

6.407

6.357

--

--

6.065

--

5.761

--

5.501

--

5.189

4.897

ID (mm)

162.74

161.47

--

--

154.05

--

146.33

--

139.73

--

131.8

124.38


 

 

 8" NB

OD = 8.625 inch (219.1 mm)

Schedule

5

10

20

30

40
STD

60

80
EH

100

120

140

160

DBL EH

ID (ins)

8.407

8.329

8.125

8.071

7.981

7.813

7.625

7.439

7.189

7.001

6.813

6.375

ID (mm)

213.54

211.56

206.38

205

202.72

198.45

193.67

188.95

182.6

177.83

173.05

161.93


 

 10" NB

OD = 10.750 inch (273 mm)

Schedule

5

10

20

30

40
STD

60

80
EH

100

120

140

160

DBL EH

ID (ins)

10.482

10.42

10.25

10.136

10.02

9.750

9.564

9.314

9.064

8.750

8.500

---

ID (mm)

266.24

264.67

260.35

257.45

254.5

247.65

242.93

236.58

230.23

222.25

215.9

---


 

 12" NB

OD = 12.750 inch (323.85 mm)

Schedule

5

10

20

30

40
STD

60

80
EH

100

120

140

160

DBL EH

ID (ins)

12.42

12.39

12.25

12.09

11.938
12.000

11.626

11.376
11.750

11.064

10.75

10.50

10.126

---

ID (mm)

315.47

314.7

311.15

307.1

303.22
304.8

295.3

288.95
298.45

281.03

273.05

266.7

257.2

---