In today’s video, Holley’s Jeremy Stoermer provides a quick, but thorough, explanation for how AN plumbing sizes are measured on behalf of Earl’s Performance.

Stoermer explains how AN plumbing gets its name from a U.S. military spec developed and agreed upon by both the Army and Navy (thus, “AN”).

Hard-line tubing sizes had already been standardized at the time, and it was the mission to mate flexible AN hose to the already standard hard-line tubing. The ways in which the two types of tubing are measured are what sometimes creates confusion.

Hard-line tubing is measured by the outer diameter (OD).

But AN hose is not. AN hose is measured by the inner diameter (ID) because it’s specifically designed to mate with hard-line tubing without causing any flow restrictions.

The outer diameter and wall thicknesses of AN hose can differ by manufacturer, so it’s important to use the correct AN hose for your job, as well as the specific fittings for that hose.

SAE fittings look very similar to AN fittings. But SAE fittings have 45-degree flares, while AN fittings have 37-degree flares which are designed to mate properly. Installation of SAE fittings when AN fittings should be used can cause leaks that nobody wants.

[NOTE: Properly torquing your AN fittings is also important. Please see our AN Fittings Torque Chart.]

Check out the video above for more information.

AN Fittings and Hose Sizes Chart

AN SizeHose / Tube O.D.SAE Thread Size
-2 1/8 in. 5/16 in.-24
-3 3/16 in. 3/8 in.-24
-4 1/4 in. 7/16 in.-20
-5 5/16 in. 1/2 in.-20
-6 3/8 in. 9/16 in.-18
-8 1/2 in. 3/4 in.-16
-10 5/8 in. 7/8 in.-14
-12 3/4 in. 1 1/16 in.-12
-16 1 in. 1 5/16 in.-12
-20 1 1/4 in. 1 5/8 in.-12
-24 1 1/2 in. 1 7/8 in.-12
-28 1 3/4 in. 2 1/4 in.-12
-32 2 in. 2 1/2 in.-12