Plumbing Fitting Converter
Convert between NPT (National Pipe Thread) and BSP (British Standard Pipe) thread sizes.
Look up thread dimensions for common pipe sizes.
Select a pipe size — see NPT and BSP thread details.
Thread Details
NPT and BSP are the two main pipe thread standards worldwide.
NPT (National Pipe Thread) — used in North America:
- Tapered threads (seal by wedging)
- 60-degree thread angle
- Uses Teflon tape or pipe dope for sealing
BSP (British Standard Pipe) — used in most other countries:
- BSPT (tapered) and BSPP (parallel) variants
- 55-degree thread angle
- Parallel threads use a washer or O-ring to seal
Common size equivalents:
| NPT Size | BSP Size | OD (in) | TPI |
|---|---|---|---|
| 1/8" | G1/8" | 0.405 | 27 |
| 1/4" | G1/4" | 0.540 | 18 |
| 3/8" | G3/8" | 0.675 | 18 |
| 1/2" | G1/2" | 0.840 | 14 |
| 3/4" | G3/4" | 1.050 | 14 |
| 1" | G1" | 1.315 | 11.5 |
| 1-1/4" | G1-1/4" | 1.660 | 11.5 |
| 1-1/2" | G1-1/2" | 1.900 | 11.5 |
| 2" | G2" | 2.375 | 11.5 |
NPT and BSP are NOT interchangeable — the thread angles differ. Adapters are needed to connect NPT to BSP fittings.