Quick size lookup
Hydraulic Hose Dash Size to ID Chart
Dash numbers use sixteenths of an inch of nominal hose bore: -8 = 8/16 = 1/2 in (12.7 mm).
Use the table below for nominal inside diameter and calculated reference flow. Search a dash number, fraction, decimal inch ID, or metric ID. Flow capacity is not a working-pressure rating.
No matching hose size found. Try a different dash number, fraction, or decimal size.
On a small screen, swipe the table sideways to see all three flow columns.
Table scrolls horizontally. Column headers remain visible while you scroll.
| Copy | ||||||
|---|---|---|---|---|---|---|
| -3 | 3/16 (0.1875) | 4.76 | 1.7 gpm | 0.9 gpm | 0.3 gpm | |
| -4 | 1/4 (0.250) | 6.35 | 3.1 gpm | 1.5 gpm | 0.6 gpm | |
| -5 | 5/16 (0.3125) | 7.94 | 4.8 gpm | 2.4 gpm | 1.0 gpm | |
| -6 | 3/8 (0.375) | 9.52 | 6.9 gpm | 3.4 gpm | 1.4 gpm | |
| -8 | 1/2 (0.500) | 12.70 | 12.2 gpm | 6.1 gpm | 2.4 gpm | |
| -10 | 5/8 (0.625) | 15.88 | 19.1 gpm | 9.6 gpm | 3.8 gpm | |
| -12 | 3/4 (0.750) | 19.05 | 27.5 gpm | 13.8 gpm | 5.5 gpm | |
| -16 | 1 (1.000) | 25.40 | 49.0 gpm | 24.5 gpm | 9.8 gpm | |
| -20 | 1-1/4 (1.250) | 31.75 | 76.5 gpm | 38.2 gpm | 15.3 gpm | |
| -24 | 1-1/2 (1.500) | 38.10 | 110.2 gpm | 55.1 gpm | 22.0 gpm | |
| -32 | 2 (2.000) | 50.80 | 195.8 gpm | 97.9 gpm | 39.2 gpm |
Important: These flow values use nominal hose inside diameter, not the toleranced actual bore, and assume uniform average velocity. Velocity limits are the 20 / 10 / 4 ft/s examples in Parker C4400-A/UK Ab-22, under its stated fluid and temperature conditions. The Parker nomogram uses UK gallons; this independently calculated table uses US gallons (or L/min). Always verify the actual hose datasheet.
Flow sizing calculator
What Hydraulic Hose Size Do I Need?
Enter the actual design flow and line type. Get the next listed dash size that meets the selected average-velocity limit.
Example at 10 US gpm: use -8 (1/2 in) for a pressure line using a 20 ft/s reference limit, -12 for return at 10 ft/s, or -20 for suction at 4 ft/s. Use the table above if the live calculator is unavailable.
A flow-velocity calculation is an initial diameter check, not a complete pressure-drop, pump-inlet, hose-assembly or safety approval.
Does Hydraulic Hose Size Refer to ID or OD?
For the hose series shown, the dash size refers to the nominal inside diameter (ID), not the outside diameter (OD). A -8 hose is nominally 8/16 in = 1/2 in ID. Its actual dimensions and tolerance depend on the manufacturer’s hose construction.
Dash size examples
-4: 4/16 = 1/4 in ID
-6: 6/16 = 3/8 in ID
-8: 8/16 = 1/2 in ID
-12: 12/16 = 3/4 in ID
-16: 16/16 = 1 in ID
Pressure, Return and Suction Hose Flow Limits
The cited Parker C4400-A/UK flow-capacity nomogram (Ab-22) labels three illustrative maximum recommended average velocities. They apply to the source’s specified hydraulic-fluid viscosity and operating-temperature assumptions.
Not a universal limit
Parker qualifies these references for hydraulic fluids of maximum viscosity 315 SSU at 38°C, used at 18–68°C. Pumps, viscosity, suction conditions, line length and allowable pressure drop may require a larger bore or a different criterion. The calculator does not evaluate pump NPSH or suction vacuum.
How to Calculate Hydraulic Hose Size From GPM
Start with the largest design flow through the hose. Select an appropriate average fluid-velocity criterion, calculate minimum bore using continuity, then choose the first available nominal hose inside diameter at or above that minimum. Never round down to a smaller dash size.
For a circular bore: D = √(4Q / πV), where Q is volumetric flow, V is average fluid velocity, A is area, and D is actual inside diameter. The calculator uses coherent units and compares the calculated bore with the 11 listed nominal sizes.
Example: 10 US gpm at 20 ft/s requires approximately 0.452 in (11.48 mm) inside diameter. A 3/8 in (-6) hose is too small for this velocity screen, so the first qualifying listed size is 1/2 in (-8). Its estimated average velocity is approximately 16.3 ft/s.
For final selection: use the actual manufacturer-specified hose bore and its tolerance; calculate pressure loss and account for hose length, fittings, fluid temperature, viscosity, operating pressure and transients.
What Hose Size for 10 GPM? Three Line Examples
1/2 in nominal ID. About 16.3 ft/s at 10 US gpm.
3/4 in nominal ID. Minimum calculated bore is about 0.639 in.
1-1/4 in nominal ID. A 1 in (-16) bore slightly exceeds 4 ft/s.
These examples all use US gallons per minute. The Parker UK nomogram’s gallon scale is imperial (UK) gallons, so the example here is not a direct copy of its numerical flow chart.
How to Select and Identify the Correct Hydraulic Hose
When specifying a new hose
- Determine governing flow and verify pressure drop at the actual ID.
- Check the exact hose/assembly working pressure, impulses and temperature rating.
- Check fluid compatibility, bend radius, abrasion, routing and vacuum suitability if relevant.
- Use fittings and crimp procedures qualified for the hose product.
When replacing an existing hose
- Read the hose layline and manufacturer’s product identification.
- Confirm nominal bore, specification, pressure rating, length and end connections.
- Do not determine dash size from outside diameter alone.
- Depressurize, isolate and follow equipment service procedures before inspection or replacement.
Dash notation is context-specific
A -8 hydraulic hose is typically 1/2 in nominal hose ID. A -8 JIC fitting refers to a fitting/tube sizing convention; it does not by itself identify a compatible hose assembly or establish working pressure.
Source, Calculation Basis and Limitations
Engineering basis reviewed October 8, 2026 · Nominal sizes -3 through -32 · Independently calculated US gpm / L/min capacities
Hose dash-size nomenclature and the 20, 10 and 4 ft/s reference velocities are taken from the Parker technical handbook. Capacity values are calculated by Turn2Engineering from nominal round-bore area and the continuity equation, not copied from Parker’s UK-gallon nomogram.
- Parker Hannifin — Hydraulic Hoses, Fittings and Equipment, Bulletin C4400-A/UKTechnical data, Ab-22, “Flow capacity nomogram”: sizes, reference velocities, source fluid and temperature conditions, UK-gallon unit note.
- SAE J1273 — Recommended Practices for Hydraulic Hose AssembliesBroader hose-assembly selection/use practice; no proprietary standard tables reproduced.
- Nominal ID convention
- Dash/16 inches for this series
- Flow capacity formula
- Q = A × V, nominal round bore
- Velocity reference
- 20 / 10 / 4 ft/s, source-qualified
- Capacity units
- US gpm, or converted L/min
- Source chart units
- UK (imperial) gallons per minute
- Excluded
- Actual-bore tolerances, pressure/impulse ratings, pressure loss, vacuum/NPSH, fluid compatibility, bend radius
- Selection range
- No nominal size suggested above -32; product sizes are not interpolated
Hydraulic Hose Size Questions
A -8 hydraulic hose has a nominal inside diameter of 8/16 in = 1/2 in = 12.7 mm. Its outside diameter and actual bore tolerance vary by hose construction.
Using the stated 20/10/4 ft/s reference velocity criteria and 10 US gpm, the smallest listed nominal IDs are -8 pressure (1/2 in), -12 return (3/4 in), and -20 suction (1-1/4 in). Final selection needs product and system checks.
The dash-size convention on this chart refers to nominal inside diameter. Measuring OD alone cannot reliably identify hydraulic hose size because reinforcement and cover thickness differ by product.
No. Dash size is a bore designation, not a pressure class. Check the selected hose/assembly’s certified working pressure, impulse rating, fluid compatibility and application limits.
No. Both use a dash number, but a JIC fitting’s nominal tube size and thread/seat geometry are separate from hose ID. Confirm the complete approved hose-and-fitting assembly.
This chart recalculates Q = A × V from nominal hose bore and the cited velocities, and deliberately labels US gallons (1 US gal = 3.785411784 L). Parker’s source nomogram labels UK/imperial gallons (1 UK gal = 4.54609 L); the two gallon definitions should not be mixed.
Hydraulic Hose Size: Key Takeaway
Find the nominal ID from the dash number first. If selecting by flow, compare the expected GPM with the pressure, return or suction velocity criterion and choose the next listed size at or above the required bore. Then verify the real hose and assembly for pressure, fluid, temperature, fittings, routing and service duty.