Plate armor thicknesses

[Dewey]

I apologize if this has already been discussed, but what are the approximate thicknesses for the various levels of plate armor from Low Tech? For example would Light Plate be equivalent to, say, 20 gauge steel, Medium Plate to 16 gauge, and Heavy Plate to 12 gauge? I realize that medieval steel was a lot worse than modern homogeneous steel, but I'd like a ballpark to figure out what DR values modern reproduction armor would have for a post-apocalyptic game I'm planning.