How to Measure Hose ID, OD and Length

What it is

A hose assembly is ordered by:

• Hose type and size: the standard and dash size printed on the layline.
• End fittings: thread type and size, seat angle and shape (straight, 45° or 90° elbow).
• Overall length: measured between set points on the fittings.
• Orientation: the offset angle between two elbow fittings. See the hose assembly orientation sheet.

How to measure

1. Read the layline. It gives the standard (such as SAE 100R2 or EN 853 2SN), the dash or ID size, and the maker. This is the best source.
2. Measure the ID at a cut end with calipers or a hose ID gauge if the layline is gone. For most hose, the dash number is the ID in sixteenths of an inch. See the Hydraulic Hose Dash Size Chart.
3. Measure the OD with calipers on the cover. Use it only to confirm a hose type in the maker's catalog. OD varies by construction.
4. Measure overall length with the hose laid straight, not coiled or pulled tight.
5. Identify both fittings using the Fitting Thread Identification Chart and the Seat Angle Identification Chart.

Where to measure overall length

Many hose shops use these points. Confirm the convention with the shop building the assembly.

Key points

• Keep the old assembly if you can. It answers most questions.
• Some hose types, such as SAE 100R5, use dash sizes based on tube OD, so the real ID is smaller than dash/16. Check the catalog.
• Hose assemblies change length slightly under pressure. Leave some slack in the route.
• Note the minimum bend radius and routing when choosing length. The maker's data gives the radius.
• Hose pressure ratings are on the maker's data sheet. Match or exceed the system's needs.

Common mistakes

• Measuring a coiled hose.
• Measuring an elbow end to its tip instead of its centerline.
• Calling the OD the dash size.
• Replacing a hose with one of a different construction because the size matched.

Governing standards: SAE J517 (hydraulic hose); SAE J1273 (recommended practices for hydraulic hose assemblies); the hose and fitting maker's catalog.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.