BSP Pipe thread sizes

Don’t fall into the trap of thinking that just because the thread measures say ¾" that it is a ¾" BSP. It is probably a ½" BSP.

For those of you trying to get your head around BSP fittings we offer the table below to help you.

A list of 15 thread sizes are defined by the BSP standards, ranging from BSP1/16 to BSP6. The BSP size number was originally based on the inner diameter measured in inches (25.4 mm) of a steel tube for which the thread was intended, but is in the modern metric version of the standard simply a size number.

BSP Thread
size

Threads
per inch

Pitch
[mm]

Major diameter
of the thread

Gauge
length
[mm]

 

Corresponding pipe

[mm]

[in]

DN

OD
[mm]

OD
[in]

Thick-
ness
[mm]

1/16

28

0.907

7.723

0.304

4

       

1/8

28

0.907

9.728

0.383

4

6

10.2

0.40

2

1/4

19

1.337

13.157

0.518

6

8

13.5

0.53

2.3

3/8

19

1.337

16.662

0.656

6.4

10

17.2

0.68

2.3

1/2

14

1.814

20.995

0.825

8.2

15

21.3

0.84

2.6

3/4

14

1.814

26.441

1.041

9.5

20

26.9

1.06

2.6

1

11

2.309

33.249

1.309

10.4

25

33.7

1.33

3.2

11

2.309

41.910

1.650

12.7

32

42.4

1.67

3.2

11

2.309

47.803

1.882

12.7

40

48.3

1.90

3.2

2

11

2.309

59.614

2.347

15.9

50

60.3

2.37

3.6

11

2.309

75.184

2.960

17.5

65

76.1

3.00

3.6

3

11

2.309

87.884

3.460

20.6

80

88.9

3.50

4

4

11

2.309

113.030

4.450

25.5

100

114.3

4.50

4.5

5

11

2.309

138.430

5.450

28.6

125

139.7

5.50

5

6

11

2.309

163.830

6.450

28.6

150

165.1

6.50

5

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Azpack
Azpack Limited, 24 Kernan Drive, Swingbridge Trading Estate, Loughborough, Leics, LE11 5JF, England. (01509) 261256