Hydraulic fitting size chart
A dash size tells you the nominal hose bore. It does not tell you the thread. Those are two different numbers, and mixing them up is the single most common cause of a wrong fitting order.
The rule that prevents most mistakes
JIC 37° flare — SAE J514 / ISO 8434-2
The default in North American mobile hydraulics. The seal is metal-to-metal on a 37° cone; no O-ring, no sealant, no washer.
| Dash | Hose bore (nom.) | Flare thread (UNF) | Typical tube OD |
|---|---|---|---|
| -04 | 1/4" | 7/16-20 | 1/4" |
| -05 | 5/16" | 1/2-20 | 5/16" |
| -06 | 3/8" | 9/16-18 | 3/8" |
| -08 | 1/2" | 3/4-16 | 1/2" |
| -10 | 5/8" | 7/8-14 | 5/8" |
| -12 | 3/4" | 1 1/16-12 | 3/4" |
| -14 | 7/8" | 1 3/16-12 | 7/8" |
| -16 | 1" | 1 5/16-12 | 1" |
| -20 | 1 1/4" | 1 5/8-12 | 1 1/4" |
| -24 | 1 1/2" | 1 7/8-12 | 1 1/2" |
| -32 | 2" | 2 1/2-12 | 2" |
ORFS — O-ring face seal, SAE J1453 / ISO 8434-3
A flat face with an O-ring recessed in the groove of the female. Better leak performance than JIC at higher pressure and in vibration, at the cost of an O-ring you can lose.
| Dash | Hose bore (nom.) | ORFS thread (UNF) |
|---|---|---|
| -04 | 1/4" | 9/16-18 |
| -06 | 3/8" | 11/16-16 |
| -08 | 1/2" | 13/16-16 |
| -10 | 5/8" | 1-14 |
| -12 | 3/4" | 1 3/16-12 |
| -16 | 1" | 1 7/16-12 |
| -20 | 1 1/4" | 1 11/16-12 |
| -24 | 1 1/2" | 2-12 |
SAE O-ring boss (ORB / SAE straight thread) — SAE J1926 / ISO 11926
This is what most people mean when they say "SAE thread". It seals with an O-ring against a machined boss face, not on the threads. Note that -04 and -06 ORB share thread sizes with JIC — but the part is not interchangeable. See JIC vs SAE.
| Dash | Port / hose bore (nom.) | ORB thread (UNF) |
|---|---|---|
| -04 | 1/4" | 7/16-20 |
| -06 | 3/8" | 9/16-18 |
| -08 | 1/2" | 3/4-16 |
| -10 | 5/8" | 7/8-14 |
| -12 | 3/4" | 1 1/16-12 |
| -16 | 1" | 1 5/16-12 |
| -20 | 1 1/4" | 1 5/8-12 |
| -24 | 1 1/2" | 1 7/8-12 |
BSP, NPT and metric — the three families that are not UNF
| Family | Seal | Common sizes | Where you meet it |
|---|---|---|---|
| BSPP (G, parallel) | Bonded washer or O-ring | G1/8, G1/4, G3/8, G1/2, G3/4, G1 | European and Japanese machinery, most imported pumps |
| BSPT (R, taper) | Thread interference + sealant | R1/8, R1/4, R3/8, R1/2 | Older equipment, steam and gas ports |
| NPT / NPTF | Thread interference | 1/8-27, 1/4-18, 3/8-18, 1/2-14, 3/4-14, 1-11.5 | US-made pumps, valves, instrumentation |
| Metric 24° cone (DKO) | Metal cone or elastomer seal | M12×1.5, M14×1.5, M16×1.5, M18×1.5, M22×1.5, M26×1.5, M30×2 | DIN 2353 / ISO 8434-1 hydraulic tube systems |
BSPP thread sizes, expanded
| BSPP (G) | Threads per inch | Major diameter (approx.) |
|---|---|---|
| G1/8 | 28 | 9.73 mm |
| G1/4 | 19 | 13.16 mm |
| G3/8 | 19 | 16.66 mm |
| G1/2 | 14 | 20.96 mm |
| G3/4 | 14 | 26.44 mm |
| G1 | 11 | 33.25 mm |
| G1 1/4 | 11 | 41.91 mm |
| G1 1/2 | 11 | 47.80 mm |
Pressure ratings: read them off the product, not off a chart
How to confirm a fitting before you order
- Measure the thread across the crests with a caliper and count threads in one inch — or use a thread pitch gauge. A 37° seat is a cone; a flat face with an O-ring is ORFS; a 24° seat is DIN/metric.
- Note the dash size separately from the thread.
- Tell us the material (carbon steel, 316 stainless, brass) and the coating you need.
- Send a photo of the mating port next to a ruler if you are unsure — we identify parts from photos every week and it is faster than guessing.
Need a part identified? Send us the photo or the drawing and we will come back with the standard, the size and a price.