BSP Thread Size Chart (BSPP and BSPT)
Look up British Standard Pipe thread sizes, parallel (BSPP, G) and taper (BSPT, R), with threads per inch, diameters and tapping drill.
BSP sizes
| Size | TPI | Major dia (mm) | Minor dia (mm) | Tap drill BSPP (mm) |
|---|---|---|---|---|
| 1/8" | 28 | 9.728 | 8.566 | 8.80 |
| 1/4" | 19 | 13.157 | 11.445 | 11.80 |
| 3/8" | 19 | 16.662 | 14.950 | 15.25 |
| 1/2" | 14 | 20.955 | 18.631 | 19.00 |
| 3/4" | 14 | 26.441 | 24.117 | 24.50 |
| 1" | 11 | 33.249 | 30.291 | 30.75 |
| 1 1/4" | 11 | 41.910 | 38.952 | 39.50 |
| 1 1/2" | 11 | 47.803 | 44.845 | 45.00 |
| 2" | 11 | 59.614 | 56.656 | 57.00 |
BSPP vs BSPT
BSPP (G, ISO 228-1): parallel, seals with a bonded washer or O ring
BSPT (R and Rc, ISO 7-1): taper 1:16, seals on the thread
G marks a parallel thread (G 1/2), R a taper male and Rc a taper female thread. Gauge diameters are the same for both forms.
Worked example
G 1/2: 14 TPI, major diameter 20.955 mm, minor 18.631 mm; common on European gauges and transmitters.
Frequently Asked Questions
What is the difference between BSPP and BSPT?
BSPP is parallel and seals with a washer; BSPT is tapered and seals on the thread.
What does G 1/2 mean?
A 1/2" BSP parallel thread to ISO 228-1.
Is 1/2" BSP the same as 1/2" NPT?
No. Both have 14 TPI but different thread angles and diameters; they do not seal together.
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