Flow-Based Selector
Find the Required Hydraulic Hose Size
Enter design flow and line type. The tool calculates the continuous bore required at the selected velocity limit, then chooses the first listed hose ID that qualifies.
Static example: At 10 US gpm in a pressure line using a 20 ft/s reference velocity, the calculated minimum bore is about 0.452 in, so the next listed size is -8 (1/2 in nominal ID).
Reference Table
Hydraulic Hose Dash Size and Flow Capacity Chart
Nominal hose IDs from -3 through -32 with Turn2Engineering-calculated flow capacities at the cited 20, 10, and 4 ft/s reference velocities.
Search by dash size, fractional inch ID, decimal ID, or millimeter ID. Capacity values are calculated from nominal bore area and average velocity; they are not hose pressure ratings.
No listed hose sizes match this search. Clear the filter or use the flow-based size selector above.
Scroll horizontally to view additional columns and vertically to view additional rows. Column headers remain visible while scrolling.
| Nominal inside diameter | Calculated flow capacity | Copy | ||||
|---|---|---|---|---|---|---|
| -3 | 3/16 in (0.188) | 4.8 mm | 1.7 gpm | 0.9 gpm | 0.3 gpm | |
| -4 | 1/4 in (0.250) | 6.3 mm | 3.1 gpm | 1.5 gpm | 0.6 gpm | |
| -5 | 5/16 in (0.312) | 7.9 mm | 4.8 gpm | 2.4 gpm | 1.0 gpm | |
| -6 | 3/8 in (0.375) | 9.5 mm | 6.9 gpm | 3.4 gpm | 1.4 gpm | |
| -8 | 1/2 in (0.500) | 12.7 mm | 12.2 gpm | 6.1 gpm | 2.4 gpm | |
| -10 | 5/8 in (0.625) | 15.9 mm | 19.1 gpm | 9.6 gpm | 3.8 gpm | |
| -12 | 3/4 in (0.750) | 19.0 mm | 27.5 gpm | 13.8 gpm | 5.5 gpm | |
| -16 | 1 in (1.000) | 25.4 mm | 49.0 gpm | 24.5 gpm | 9.8 gpm | |
| -20 | 1-1/4 in (1.250) | 31.8 mm | 76.5 gpm | 38.2 gpm | 15.3 gpm | |
| -24 | 1-1/2 in (1.500) | 38.1 mm | 110.2 gpm | 55.1 gpm | 22.0 gpm | |
| -32 | 2 in (2.000) | 50.8 mm | 195.8 gpm | 97.9 gpm | 39.2 gpm | |
Scope: Flow capacities use nominal hose ID and Q = AV. The Parker source nomogram itself labels UK gallons; this Turn2Engineering table instead reports independently calculated US gpm and L/min values from the same cited velocity criteria. Do not use these values as working-pressure, impulse, temperature, vacuum, or product-capacity ratings.
Nomenclature
What Hydraulic Hose Size Measures
For the size series on this page, the dash designation represents nominal hose inside diameter in sixteenths of an inch.
- Recommended dash size
- -8
- Nominal ID
- 1/2 in (12.7 mm)
- Meaning
- Inside diameter
Pressure, Return, and Suction Velocity Guidance
The Parker flow-capacity nomogram marks maximum recommended velocities of 20 ft/s for pressure lines, 10 ft/s for return lines, and 4 ft/s for suction lines. Parker qualifies those recommendations for hydraulic fluids with maximum viscosity 315 S.S.U. at 38°C, working at room temperature from 18°C to 68°C.
Important limitation
These are source-specific sizing references, not universal allowable velocities. OEM, pump-inlet, fluid, temperature, hose-construction, noise, pressure-drop, or reliability requirements may justify a larger hose.
How Hydraulic Hose Dash Sizes and Flow Sizing Work
Parker describes dash size as the hose inner diameter in sixteenths of an inch. For example, -8 corresponds to 8/16 in = 1/2 in nominal ID. The selector first calculates the bore required by the continuity relationship, then steps up to the first listed nominal size that keeps average velocity at or below the chosen criterion.
Why flow velocity changes the required hose size
For a fixed flow rate, reducing inside diameter reduces flow area and increases average velocity. That can increase pressure loss and heat, and inlet lines can be particularly sensitive to excessive velocity. The sizing relationship is:
For a circular bore: D = √(4Q / πV). The calculator converts values to SI internally, solves for D, and then selects the next qualifying listed hose ID.
How to use this chart
- Enter the design flow rate, not an arbitrary average if the circuit has a higher governing flow.
- Choose pressure, return, or suction according to the line being sized.
- Read the calculated minimum bore and the first listed dash size that qualifies.
- Verify the chosen product separately for pressure, impulse duty, fluid compatibility, temperature, bend radius, fittings, routing, and suction/vacuum requirements.
Hydraulic Hose Sizing Examples
10 US gpm pressure line
Assumption: 20 ft/s reference velocity.
The continuous bore required is about 0.452 in. A -6 hose is only 0.375 in, so the first listed size that qualifies is -8 (0.500 in).
Check: Average velocity in -8 is about 16.3 ft/s, below the 20 ft/s criterion. Parker’s own nomogram example also steps from above -6 to -8 at its 10-gallon-per-minute example point; the Parker chart labels UK gallons, while this page’s calculator uses US gpm.
10 US gpm return line
Assumption: 10 ft/s reference velocity.
The required bore is about 0.639 in. A -10 hose is 0.625 in and is slightly too small under strict first-qualifying logic, so the selector steps to -12 (0.750 in).
Check: Do not round the required diameter down to the nearest dash size.
10 US gpm suction line
Assumption: 4 ft/s reference velocity.
The required bore is about 1.011 in. A -16 hose is 1.000 in and produces about 4.09 ft/s, so it does not meet a strict 4 ft/s ceiling. The next listed size is -20 (1.250 in).
Check: Suction-line design can be governed by pump inlet requirements that are more restrictive than a generic velocity screen.
Hose Size Is Not a Pressure Rating
Nominal ID answers a flow-area question; it does not identify a hose’s allowable working pressure. Two hoses with the same -8 nominal ID can have very different reinforcement, working-pressure, impulse, temperature, bend-radius, fluid-compatibility, and vacuum characteristics.
After selecting ID
- Verify the exact hose product’s working pressure and impulse capability.
- Check fluid and temperature compatibility.
- Confirm bend radius, routing, abrasion protection, and assembly length.
- Verify fittings as a compatible hose-and-fitting system.
Identifying an existing hose
Use the hose layline or manufacturer identification first. Measuring outside diameter alone cannot establish dash size because wall construction varies. Never cut, loosen, or measure a hose while the hydraulic system is pressurized.
Dash-number caution
Hose dash size on this page refers to nominal hose ID. A JIC fitting dash designation is not, by itself, proof of hose ID, thread, seat, or assembly compatibility.
Source, Method, and Data Limitations
Source basis checked August 16, 2026 · Dataset label: T2E Hydraulic Hose Nominal ID & Velocity Capacity — Parker-Based 2026
The nominal dash/ID series and velocity guidance are anchored to Parker’s Flow Capacity Nomogram. Turn2Engineering calculates the flow-capacity values independently from nominal circular bore area and Q = AV. The source nomogram is cited, not reproduced.
- Parker Hannifin — Hydraulic Hoses, Fittings and Equipment, Technical Handbook, Bulletin C4400-A/UK Evidence locator: Technical data Ab-22, “Flow capacity nomogram.” Supports dash/ID series, 20/10/4 ft/s reference velocities, example selection logic, and source conditions.
- SAE International — SAE J1273, Recommended Practices for Hydraulic Hose Assemblies Used only for broader hose-assembly selection/use context. This page does not reproduce SAE tables or standards text.
- Parker Hannifin — Copyright Release for Website Download Rights basis for avoiding reproduction of Parker’s nomogram artwork or proprietary catalog arrangement.
Dataset and Source-Check Details
- Publisher
- Turn2Engineering
- Primary source locator
- Parker C4400-A/UK, Ab-22
- Supported nominal range
- -3 through -32
- Calculated fields
- Flow capacities, required bore, resulting velocity, velocity margin
- Reference conditions
- Maximum viscosity 315 S.S.U. at 38°C; room temperature 18–68°C for the cited Parker velocities
- Interpolation
- Continuous bore is calculated; listed dash sizes are never interpolated
- Extrapolation
- No recommendation beyond -32 / 2 in within this chart
- Download rights
- Full CSV disabled; visible result/row copying only
Hydraulic Hose Size FAQ
It depends on line type: with this page’s cited velocity criteria, 10 US gpm selects -8 for a pressure line, -12 for a return line, and -20 for a suction line under strict first-qualifying logic.
For the hose-size series used here, -8 means a nominal inside diameter of 8/16 in, or 1/2 in.
The dash convention used on this page refers to nominal hose inside diameter; outside diameter varies with hose construction.
No. Working pressure depends on the specific hose product, reinforcement, fittings, temperature, fluid, and operating duty, not nominal ID alone.
No. Dash notation is used in both contexts, but a fitting designation does not by itself establish hose ID, thread size, seat geometry, or compatibility.
Use Flow to Size the Bore, Then Verify the Hose Product
Use the calculator to determine the minimum bore from flow and a documented velocity criterion, then step up to the first listed dash size that qualifies. Treat that result as an ID-sizing screen—not final hose approval—and verify the exact hose, fittings, pressure, temperature, fluid, routing, and duty for the application.