Can somebody tell me how to measure AN fitting sizes? Can you measure them with a ruler or tape measure and then convert that to something else?

 

Measure the tubing size on the back side of the fitting. The -AN number is how many 1/16" it is. 3/8" = 6AN. 1/2" = 8AN. 5/8" = 10AN. You can also try different sized SAE wrenches. Subtract 5/16" from the wrench size to get the fitting size, then convert to -AN by dividing by 16ths. So, if a 15/16" wrench fits, subtract 5/16", which gives you 10/16", which would be a 10AN. The wrench size rule works for most fittings, but some brands may have weird head sizes.

 

Wow, didn't know that! That's cool!