*Mods this might be a usefull thread to put in a faq thread*
OK,
Took a bit but I made up this chart using summit racings website info
This chart is made to be the link between the AN standard and conventional measure. This will help allot when selecting hoses and fittings for your turbo coolant, and oil lines as well as some of you over achievers that want it for fuel and main coolant lines!!


AN tubing info: rubber line with stainless steel cover
-3 AN Hose Inside Diameter (in): 0.140 in. Hose Outside Diameter (in): 0.375 in.
-4 AN Hose Inside Diameter (in): 0.218 in. Hose Outside Diameter (in): 0.438 in.
-5 AN Hose Inside Diameter (in): 0.250 in. Hose Outside Diameter (in): 0.500 in.
-6 AN Hose Inside Diameter (in): 0.343 in Hose Outside Diameter (in): 0.547 in.
-7 AN Hose Inside Diameter (in): 0.375 in. Hose Outside Diameter (in): 0.625 in.
-8 AN Hose Inside Diameter (in): 0.438 in. Hose Outside Diameter (in): 0.641 in
-9 AN Hose Inside Diameter (in): 0.500 in. Hose Outside Diameter (in): 0.718 in.
-10 AN Hose Inside Diameter (in): 0.563 in. Hose Outside Diameter (in): 0.797 in.
-11 AN Hose Inside Diameter (in): 0.620 in. Hose Outside Diameter (in): 0.875 in.
-12 AN Hose Inside Diameter (in): 0.690 in. Hose Outside Diameter (in): 0.940 in.
-14 AN Hose Inside Diameter (in): 0.750 in. Hose Outside Diameter (in): 1.031 in.
-16 AN Hose Inside Diameter (in): 0.875 in. Hose Outside Diameter (in): 1.125 in.
-18 AN Hose Inside Diameter (in): 1.000 in. Hose Outside Diameter (in): 1.312 in.
-20 AN Hose Inside Diameter (in): 1.125 in. Hose Outside Diameter (in): 1.437 in.
-24 AN Hose Inside Diameter (in): 1.340 in. Hose Outside Diameter (in): 1.703 in.
-28 AN Hose Inside Diameter (in): 1.500 in. Hose Outside Diameter (in): 1.828 in.
-32 AN Hose Inside Diameter (in): 1.750 in. Hose Outside Diameter (in): 2.125 in.
Info thanks to summit racing

Now this doesn’t insure that the fittings will have the same ID openings but it will give you a good Idea.