Hydraulic hose sizes by dash number
The dash number is the hose inside diameter in sixteenths of an inch. Divide by 16 and you have the ID. It is stamped on the layline along with the SAE spec and the working pressure.
The flow columns show what each size carries at the recommended velocity for that job. Undersize a pressure line and you generate heat and pressure drop; undersize a suction line and you cavitate the pump.
| Dash | ID (in) | ID (mm) | Pressure line at 20 ft/s (gpm) | Suction line at 4 ft/s (gpm) |
|---|---|---|---|---|
| -04 | 1/4 | 6.4 | 3.1 | 0.6 |
| -05 | 5/16 | 7.9 | 4.8 | 1.0 |
| -06 | 3/8 | 9.5 | 6.9 | 1.4 |
| -08 | 1/2 | 12.7 | 12.2 | 2.4 |
| -10 | 5/8 | 15.9 | 19.1 | 3.8 |
| -12 | 3/4 | 19.0 | 27.5 | 5.5 |
| -16 | 1 | 25.4 | 49.0 | 9.8 |
| -20 | 1 1/4 | 31.8 | 76.5 | 15.3 |
| -24 | 1 1/2 | 38.1 | 110.2 | 22.0 |
| -32 | 2 | 50.8 | 195.9 | 39.2 |
Hydraulic hose sizing by flow rate
Enter your flow and the line type and this returns the smallest dash size that keeps velocity inside the recommended band. If the answer sits between two sizes, go up.
- Smallest suitable hose
- -08 (0.5 in ID)
Runs at 16.3 ft/s, inside the pressure line at 20 ft/s limit. Go one size up if the run is long or has many bends.
Hydraulic fitting size chart
Fitting dash sizes follow the same sixteenths rule, but the thread on the end of the fitting is a separate number and does not match the hose dash. A -08 JIC fitting has a 3/4-16 thread, not a 1/2 inch one.
| Dash | Hose ID (in) | JIC 37° thread | SAE ORB thread |
|---|---|---|---|
| -04 | 1/4 | 7/16-20 | 7/16-20 |
| -06 | 3/8 | 9/16-18 | 9/16-18 |
| -08 | 1/2 | 3/4-16 | 3/4-16 |
| -10 | 5/8 | 7/8-14 | 7/8-14 |
| -12 | 3/4 | 1 1/16-12 | 1 1/16-12 |
| -16 | 1 | 1 5/16-12 | 1 5/16-12 |
| -20 | 1 1/4 | 1 5/8-12 | 1 5/8-12 |
| -24 | 1 1/2 | 1 7/8-12 | 1 7/8-12 |
Metric hydraulic fittings
Metric hydraulic fittings are specified by thread size and pitch, and by whether the cone is 24 degrees (DIN 2353, light or heavy series) or 60 degrees (BSP). The two are not interchangeable and a 24 degree cone in a 60 degree seat will leak under pressure.
DIN light series (L) suits pressures to around 315 bar depending on size, heavy series (S) goes higher. The tube OD, not the hose ID, sets the fitting size on DIN tube ends.
| Tube OD (mm) | Thread | Nearest hose dash |
|---|---|---|
| 6 | M12x1.5 | -04 |
| 8 | M14x1.5 | -04 |
| 10 | M16x1.5 | -05 |
| 12 | M18x1.5 | -06 |
| 15 | M22x1.5 | -08 |
| 18 | M26x1.5 | -10 |
| 22 | M30x2 | -12 |
| 28 | M36x2 | -16 |
| 35 | M45x2 | -20 |
| 42 | M52x2 | -24 |
