Hydraulic Fitting Size Chart — NPT, JIC, BSP & Metric | koeedmro
GUIDE
Step 1 — Measure the Thread
- Measure the male thread OD (calipers, mm).
- Count threads per inch or measure pitch in mm.
- Check the sealing method: taper, 37°/45° cone, bonded washer, or O-ring.
Thread Identification Tables
| Type | Size | Male OD | Pitch / TPI | Sealing |
|---|---|---|---|---|
| NPT (taper 60°) | 1/8" | 10.3 mm | 27 TPI | Taper interference |
| NPT | 1/4" | 13.2 mm | 18 TPI | Taper interference |
| NPT | 3/8" | 16.7 mm | 18 TPI | Taper interference |
| NPT | 1/2" | 21.0 mm | 14 TPI | Taper interference |
| NPT | 3/4" | 26.4 mm | 14 TPI | Taper interference |
| NPT | 1" | 33.2 mm | 11.5 TPI | Taper interference |
| JIC 37° | -4 (7/16-20) | 11.1 mm | 20 TPI | 37° cone seat |
| JIC 37° | -6 (5/8-18) | 14.3 mm | 18 TPI | 37° cone seat |
| JIC 37° | -8 (3/4-16) | 19.1 mm | 16 TPI | 37° cone seat |
| JIC 37° | -10 (7/8-14) | 22.2 mm | 14 TPI | 37° cone seat |
| JIC 37° | -12 (1-1/16-12) | 26.9 mm | 12 TPI | 37° cone seat |
| JIC 37° | -16 (1-5/16-12) | 33.3 mm | 12 TPI | 37° cone seat |
| BSP 55° (G) | G1/8 | 9.7 mm | 28 TPI | Bonded seal / cone |
| BSP 55° (G) | G1/4 | 13.2 mm | 19 TPI | Bonded seal / cone |
| BSP 55° (G) | G3/8 | 16.7 mm | 19 TPI | Bonded seal / cone |
| BSP 55° (G) | G1/2 | 20.9 mm | 14 TPI | Bonded seal / cone |
| BSP 55° (G) | G3/4 | 26.4 mm | 14 TPI | Bonded seal / cone |
| BSP 55° (G) | G1 | 33.3 mm | 11 TPI | Bonded seal / cone |
| Metric 24° (DIN) | M12×1.5 | 12 mm | 1.5 mm | 24° cone + O-ring |
| Metric 24° (DIN) | M14×1.5 | 14 mm | 1.5 mm | 24° cone + O-ring |
| Metric 24° (DIN) | M16×2 | 16 mm | 2 mm | 24° cone + O-ring |
| Metric 24° (DIN) | M22×1.5 | 22 mm | 1.5 mm | 24° cone + O-ring |
JIC vs BSP trap: 1/2" sizes look similar — JIC is 37° cone at 20 TPI, BSP is 55° at 14 TPI. They never seal together; verify by thread engagement, not OD alone.
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FAQ
How do I tell NPT from BSP?
Similar ODs but different forms: NPT is 60° taper, BSP is 55°. They never seal reliably together. Use a thread gauge for the angle check.
What is a -6 JIC fitting?
The dash number is the tube OD in sixteenths of an inch: -6 = 6/16 = 3/8" tube, with a 5/8-18 UNF thread and a 37° cone seat.
Can I mix JIC and BSP hoses?
Not reliably — cone angles and threads differ. Use a purpose-made adapter and confirm pressure rating.