A hydraulic hose that is one size off will leak, kink, or fail early. Getting the measurement right is simple once you know the three numbers that define every assembly: inside diameter, outside diameter, and length.

Is Hydraulic Hose Measured by ID or OD?

Hydraulic hose is sized by inside diameter (ID). ID controls flow and is the number that must match the fitting stem. Outside diameter matters for routing, clamps, and guards, but it does not define the hose size. Measure ID at the cut end of the hose or read the layline printed on the cover.

Understanding Dash Sizes

Hydraulic hose and fittings use dash sizes, where the dash number is the ID in sixteenths of an inch. A -8 hose is 8/16, or 1/2 inch ID. A -16 hose is 16/16, or 1 inch ID. Fittings follow the same system, so a -8 hose pairs with a -8 fitting. Keep a dash chart handy to avoid mix-ups.

How to Measure a Replacement Hose

• ID and dash size: read the layline or measure the bore at the cut end.
• Length: measure from the sealing surface of one fitting to the sealing surface of the other, not tip to tip.
• Fittings: note the end type (JIC, ORFS, NPT, SAE, flange), thread size, and the orientation of any elbows.

Match Pressure and Bend Radius

Confirm the working pressure rating meets or exceeds your system, and respect the minimum bend radius so the hose does not kink at the fittings. When in doubt, bring the old assembly and let us match it.

We build and pressure-test hydraulic assemblies in metric and standard sizes, usually same day. See our hydraulic hose service or request a quote.