What Is a BSPT Thread?

BSPT stands for British Standard Pipe Tapered. Unlike NPT (the U.S. standard), BSPT threads are tapered at a 1:16 ratio and feature a 55-degree thread angle. They are widely used in hydraulic systems, fluid power equipment, and industrial machinery imported from Europe, Asia, Australia, and the UK.

 

At Gear House Hydraulics, we stock a full range of BSPP/BSPT Fittings including the 7000 JIC to BSPT, 7100 Male JIC to Male BSPT 45° Elbow, 7200 Male JIC to Male BSPT Elbow 90°, and many more making it easy to find the right adapter once you have identified your thread size.

 

BSPT vs. NPT: Key Differences

⚠ WARNING: BSPT and NPT threads are NOT interchangeable. They have different thread angles (55° vs. 60°) and different pitches. Mixing them causes leaks, thread damage, and potential system failure.

 

Feature	BSPT	NPT
Thread Angle	55°	60°
Taper Ratio	1:16	1:16
Standard	ISO 7-1 / EN 10226	ANSI/ASME B1.20.1
Common Regions	UK, Europe, Asia, Australia	USA, Canada
Sealing Method	Thread interference + sealant	Thread interference + sealant

 

Tools You Will Need

•       Digital calipers (measures OD and ID in inches or mm)

•       Thread pitch gauge (confirms threads per inch)

•       Thread angle gauge or profile gauge (verifies 55° angle)

•       Pen and paper to note your measurements

 

PRO TIP: You can find these tools at any industrial supply store. A digital caliper is the most important tool — do not try to estimate by eye.

 

Step-by-Step: How to Measure BSPT Thread

Step 1: Confirm the Thread Is Tapered

Look at the thread from the side. BSPT threads get visibly narrower (taper) toward the end of the fitting. If the diameter stays the same along the length, it is BSPP (parallel), not BSPT.

 

PRO TIP: Use your caliper to measure the OD at two different points along the thread. If the measurements differ, the thread is tapered (BSPT or NPT).

 

Step 2: Measure the Inner Diameter (ID)

Because BSPT threads are tapered, the outer diameter changes along the fitting length  making OD unreliable for identification. Instead, measure the inner bore diameter (ID) using your caliper.

 

1.    Open your caliper jaws and insert the smaller measuring tips into the bore of the fitting.

2.    Expand the jaws until they contact the bore wall on both sides.

3.    Read the measurement in inches.

4.    This ID corresponds to the nominal pipe size for example, an ID of 0.375" = 3/8" BSPT.

 

Step 3: Count Threads Per Inch (TPI)

Use your thread pitch gauge or count manually:

5.    Place the fitting against a ruler.

6.    Count the number of thread crests (peaks) over a 1/4" span.

7.    Multiply that number by 4 to get threads per inch (TPI).

8.    Cross-reference TPI with the size chart below.

 

Step 4: Verify the 55° Thread Angle

Use a thread angle gauge or profile gauge to confirm the thread angle is 55°. This distinguishes BSPT from NPT, which has a 60° angle. If you do not have a gauge, a trained eye can often spot the difference by comparing to a known fitting.

 

Step 5: Match Your Measurements to the Size Chart

Use the table below to confirm the exact BSPT thread size based on your ID measurement and TPI count.

 

BSPT Thread Size Reference Chart

Nominal Size	OD (Thread Root)	TPI	Angle	ISO Designation
1/16"	7.723 mm (0.304")	28	55°	R 1/16
1/8"	9.728 mm (0.383")	28	55°	R 1/8
1/4"	13.157 mm (0.518")	19	55°	R 1/4
3/8"	16.662 mm (0.656")	19	55°	R 3/8
1/2"	20.955 mm (0.825")	14	55°	R 1/2
3/4"	26.441 mm (1.041")	14	55°	R 3/4
1"	33.249 mm (1.309")	11	55°	R 1
1-1/4"	41.910 mm (1.650")	11	55°	R 1-1/4
1-1/2"	47.803 mm (1.882")	11	55°	R 1-1/2
2"	59.614 mm (2.347")	11	55°	R 2

 

Gear House Hydraulics BSPP/BSPT Fittings

Once you have identified your BSPT thread size, Gear House Hydraulics offers a wide selection of steel and stainless steel BSPT adapters and fittings to fit your system. Below are some of the most commonly ordered products from our BSPP/BSPT collection:

 

Part Number	Description	Connection Type
7000	JIC to BSPT Straight	JIC Male × BSPT Male
7022	JIC Swivel to BSPP Straight	JIC Swivel × BSPP Male
7023	BSPP Swivel to JIC Swivel Straight	BSPP × JIC Swivel
7032	BSPP to NPTF Straight	BSPP Male × NPTF Male
7042	BSPP to Female NPTF Pipe	BSPP Male × NPTF Female
7042-BS	Male BSPP to Female NPTF — With Bonded Seal	BSPP × NPTF + Seal
7100	Male JIC to Male BSPT 45° Elbow	JIC Male × BSPT Male
7102	Male JIC to Male BSPP Elbow 45° — Bonded Seal	JIC Male × BSPP Male
7200	Male JIC to Male BSPT Elbow 90°	JIC Male × BSPT Male
7202	Male JIC to BSPP 90° Elbow — Bonded Seal	JIC Male × BSPP Male
9022	Male BSPP to Male BSPP Union	BSPP × BSPP Union
9024	BSPP to Female BSPP Swivel Straight	BSPP Male × BSPP Female Swivel
9522-P	Male BSPP Hex Head Plug — 60° Seat	BSPP Male Plug
9900	Bonded Seal Buna-N for BSPP Fittings	Sealing Washer

 

Common Mistakes to Avoid

•       Confusing BSPT with NPT — they look similar but are NOT compatible. Always verify the 55° thread angle.

•       Measuring OD on a tapered thread — OD changes along BSPT fittings. Always use ID for BSPT identification.

•       Estimating thread count without a gauge — a one-TPI error means the wrong fitting.

•       Assuming BSPT and BSPP are the same — BSPT is tapered, BSPP is parallel. They require different sealing methods.

•       Forcing mismatched threads — this damages both male and female threads and causes leaks.

 

Need Help Identifying Your Thread?

Not sure what you have? Our technical team at Gear House Hydraulics is here to help. Contact us and we will identify the correct fitting for your application: