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Understanding BSP Sizing

How to Measure Your BSP Fittings

When it comes to finding the correct thread fitting it can be confusing especially when some brands/manufacturers make a bespoke thread size unique to their own products. meaning any replacement parts will have to be purchased directly from them ensuring the after-sale.

however, most of the threads used on the market are BSP (British Standard Pipe) threads, making them universal from products, brands and manufacturers because they are all manufactured to the same specification

When checking and replacing your couplings or 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.

Now you know the BSP thread size you are looking for have a look at our threaded fitting range We stock everything from rigid pipe converters to multi-stepped hosetails for flexi hose

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