It should come as no surprise that even within full grain and top grain leather, there are a lot of variations from one piece of leather to the other. Some of these are purely aesthetic, such as the color it has been dyed. Some, however, can play a big part in what your product is like. One of the most prominent of these, especially if you are interested in doing your own leather working, either commercially or as a hobby, is leather weight and thickness.
So which is it measured in, weight or thickness?
The answer is both! They are fairly interchangeable, but usually the thickness is denoted by the weight, since the leather is cut while it is still wet, and the cut isn’t precisely even all across the hide. You will most commonly find leather measured in ounces, so let’s break that down to relative thickness. You can measure leather with what is called a leather gauge, pictured to the right. The inside numbers are ounces, and the outside numbers are millimeters. You can use your own leather gauge to check our math, or your particular piece of leather, but we have found that 1 oz is roughly equal to .4 mm. So if you hear that a piece of leather is 6 oz, then you can know that it will be around 2.4 mm thick, which is a pretty solid piece of leather.
Why does it matter?
Since most leather crafters will handle this for you, this matters the most if you are working with leather yourself.You are going to have a really hard time folding your wallet if you make it out of leather that is 9 oz(or nearly 4mm thick). Tandy Leather is one of the best resources on learning to work leather on your own, and they have a great infographic on uses for various leather weights here. They recommend 9-10 oz leather for things like holsters, belts, and saddlebags, whereas they reserve the 1-2 oz leathers for linings and embossing. You can see why it would be a problem if you are making your saddlebags out of the lining of a purse, or vice versa. None of these varieties are necessarily better than the other. They just have different purposes that they are good for. Think of it like a jacket. Some days you may want a light jacket, other days you may want a heavy winter coat. Both of them would create an absolutely miserable experience in the wrong setting.
What does this mean for me?
Become familiar with your product. Once again, this is especially important if you are wanting to make your own leather products. The more you work with leather the more natural it will become to identify what leather should be used for what products. There have been times where I have grabbed a piece of leather to make a wallet, and without even feeling it my dad has been able to tell me “That leather is too thick for what you’re wanting to do with it”. And with over 20 years of leather experience, it is no surprise that he was right. Over time, you can be that way too.