British Standard Pipe (BSP) Thread Chart
Industry Standard: ISO 228 / ISO 7
British Standard Pipe (BSP) threads are the international standard pipe thread fittings used throughout Europe, Asia, and Australia. BSP threads include both parallel (G / ISO 228) and tapered (R / ISO 7) series, using a Whitworth 55-degree thread angle profile.
| Size | Ø Major (in) | TPI | Pitch (in) | Ø Pitch (in) | Ø Minor (in) | Tap Drill |
|---|---|---|---|---|---|---|
| G 1/8 | 0.3830 | 28 | 0.03571 | 0.3601 | 0.3373 | 8.8 mm |
| G 1/4 | 0.5180 | 19 | 0.05263 | 0.4843 | 0.4506 | 11.8 mm |
| G 3/8 | 0.6560 | 19 | 0.05263 | 0.6223 | 0.5886 | 15.0 mm |
| G 1/2 | 0.8250 | 14 | 0.07143 | 0.7793 | 0.7335 | 18.6 mm |
| G 5/8 | 0.9020 | 14 | 0.07143 | 0.8563 | 0.8105 | 20.4 mm |
| G 3/4 | 1.0410 | 14 | 0.07143 | 0.9953 | 0.9495 | 24.3 mm |
| G 7/8 | 1.1890 | 14 | 0.07143 | 1.1433 | 1.0975 | 27.9 mm |
| G 1" | 1.3090 | 11 | 0.09091 | 1.2508 | 1.1926 | 30.5 mm |
| G 1-1/4 | 1.6500 | 11 | 0.09091 | 1.5918 | 1.5336 | 39.2 mm |
| G 1-1/2 | 1.8820 | 11 | 0.09091 | 1.8238 | 1.7656 | 45.1 mm |
| G 2" | 2.3470 | 11 | 0.09091 | 2.2888 | 2.2306 | 56.7 mm |
| G 2-1/2 | 2.9600 | 11 | 0.09091 | 2.9018 | 2.8436 | 72.1 mm |
| G 3" | 3.4600 | 11 | 0.09091 | 3.4018 | 3.3436 | 84.8 mm |
| G 4" | 4.4500 | 11 | 0.09091 | 4.3918 | 4.3336 | 109.1 mm |
Standard FAQs
What is the difference between BSP parallel (G) and BSP tapered (R)?
BSP parallel threads (G) do not seal on the threads themselves and require a washer or O-ring. BSP tapered threads (R/Rc/Rp) seal by metal-to-metal contact on the threads, similar to NPT.
What thread angle do BSP threads use?
BSP threads use the British Whitworth standard 55-degree thread angle, compared to the 60-degree angle used by NPT and metric threads.