varadin wrote:12 ounce leather is what people are told to buy by people not understanding the rules or not understanding leather.
I wouldn't go that far. Leather is sold by the ounce, so it'll be much easier to look for something that is 12 oz. vs 3/16", especially if you don't have the luxury of a local leather store.
The real issue that people should realize is that leather is a natural product, so there will inevitably be variance in thickness. A side of leather marked as 12 oz. will
average 3/16" thick. It will not be of uniform thickness throughout the whole piece. In fact, some sections will likely dip down to 8 oz. (2/16" for easy comparison), while some could exceed 14 oz. Long story short, you are safe buying 12 oz. leather, but be aware that some sections of the hide will be unusable as straight armor grade leather. The percentage that is below 3/16" thick will vary, so do as Varadin suggests and take calipers if you want to be sure.