Have you ever needed to convert leather and found it difficult to get from one measurement type to another? You know, from oz. to fractional inches for example? It happens to me all the time (especially when ordering leather online), so I finally put together a couple of conversion charts for the leather thicknesses I use the most.
Leather suppliers usually describe their leather in oz. thickness, but the way I measure leather in the workshop is with a pair of digital calipers (which gives me the thickness in mm). These charts allow me to figure out right away that a 2.5 ounce leather will be about 1mm thick.
There are 2 versions of the chart: one with bands marking the oz. lines, one with bands highlighting the mm. These only cover leather from 1 to 4 mm thick - that's everything from a very lightweight lamb (0.7mm) or pig leather to a very thick bullhide (3.5-4oz.). Of course, many vegetable-tanned leathers can be thicker than 4mm, but I decided to leave that for another chart. Think of these as more for light, medium and heavy-weight garment or chrome-tanned hides that can be sewn with a typical industrial leather sewing machine.