How To's

How to Measure Your BSP Fittings

When checking and replacing your couplings and fittings, you will need to know how to measure their BSP (British Standard Pipe) threads. These can be BSPP, where they are parallel, sealed by a washer or an ‘O’ ring seal or BSPT, where they are tapered along their length, sealing with mating male and female threads. 

This is a common confusion leading customers to question the replacement and spare parts that they actually need for their machine. We want to help abolish this ambiguity in choosing your correct couplings, so take a look at the measurement guide below so you know exactly what to look for.

First, to determining the thread size:

  • Measure the outer diameter (OD) of the thread (in inches)

  • Then subtract 25% from this (¼ inch)

  • Therefore, if the OD of a BSP thread measures 1”, the thread size will be ¾ . This is often written in shorthand as a Dash Size and this particular one would be written as -12.

  • You’ll then need to make sure it is a BSP fitting so by counting the threads on your coupling, perhaps only just over ¼”, you can just multiply this by four to find the threads per inch. You can then match this measurement against the table below, to find the exact dimensions for your fittings.

BSP Thread Size

Outside Diameter mm / inch

TPI

1/16 Inch BSP

7.7 mm / 0.304"

28

1/8 Inch BSP

9.7 mm / 0.383"

28

1/4 Inch BSP

13.16 mm / 0.518"

19

3/8 Inch BSP

16.66 mm / 0.656"

19

1/2 Inch BSP

20.99 mm / 0.825"

14

5/8 Inch BSP

22.99 mm / 0.902"

14

3/4 Inch BSP

26.44 mm / 1.041"

14

7/8 Inch BSP

30.20 mm / 1.189"

14

1 Inch BSP

33.25 mm / 1.309"

11

1-1/4 Inch BSP

41.91 mm / 1.650"

11

1-1/2 Inch BSP

47.80 mm / 1.882"

11

2 Inch BSP

59.61 mm / 2.347"

11

2-1/4 Inch BSP

65.71 mm / 2.587"

11

2-1/2 Inch BSP

75.18 mm / 2.96"

11

3 Inch BSP

87.88 mm / 3.46"

11

4 Inch BSP

113.03 mm / 4.45"

11

5 Inch BSP

138.43 mm / 5.45"

11

6 Inch BSP

163.83 mm / 6.45"

11

Now you know which couplings you need, check out our wide range of fittings by clicking the button below: