Guide
NPT vs BSPT: how to tell the two pipe threads apart
NPT and BSPT are both tapered pipe threads, and both are common on UAE sites. They look alike, but they have a different thread angle and, at most sizes, a different number of threads per inch.
The two differences that matter
- Thread angle: NPT is 60°, BSPT is 55°.
- Threads per inch (TPI): different at most sizes, the same at ½" and ¾".
Threads per inch by size
| Size | NPT (TPI) | BSPT (TPI) |
|---|---|---|
| ⅛" | 27 | 28 |
| ¼" | 18 | 19 |
| ⅜" | 18 | 19 |
| ½" | 14 | 14 |
| ¾" | 14 | 14 |
| 1" | 11.5 | 11 |
| 1¼" | 11.5 | 11 |
| 1½" | 11.5 | 11 |
| 2" | 11.5 | 11 |
| Thread angle | 60° | 55° |
A simple way to tell them apart
Use a thread pitch gauge. At ⅛", ¼", ⅜" and 1" to 2", count the threads per inch: the gauge that sits cleanly in the thread tells you NPT or BSPT straight away.
At ½" and ¾", both threads have 14 TPI, so counting will not help. Check the thread angle instead with a 55° and a 60° gauge: the one that fits the thread profile with no gap is the answer.
If you have no gauge, bring the part or a fitting that screws onto it to our counter and we will check it with you.
Why you should not mix them
At ½" and ¾" an NPT part may screw a few turns into a BSPT part, because the pitch is the same. The thread angles still differ, so the flanks do not seal and the joint can leak under pressure. Do not rely on extra tape or sealant to make a mixed joint hold. Match the thread instead.
Order the right thread
Many of our items are listed in both: brass, bronze and S.S threaded ball and gate valves (BSP or NPT), forged S.S and C.S Y-strainers (BSP or NPT), S.S forged threaded fittings (BSP or NPT), C.S swage nipples (BSP or NPT), and camlock types A, B, D and F (BSPT or NPT). Tell us which thread you need on WhatsApp, and for pipe threading at the counter, tell us the thread type before you come.
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Questions buyers ask
Can NPT and BSPT fittings be screwed together?
At ½" and ¾" they may engage a few turns, but they do not seal reliably. Use matching threads.
How do I check a ½" thread?
Use a 55° and a 60° thread gauge, because both NPT and BSPT have 14 TPI at that size.
Do you sell fittings in both threads?
Yes. Many of our valves and fittings are listed in NPT and BSPT. Tell us which one you need when you send your list.
Send us your list
Sizes, rating, end connection and quantity. We reply with stock and a price.