If you don't make your living with your tools, and you didn't major in math, maybe you too have trouble with SAE wrench and drill sizes. Metric is a no brainer....if you reach for a 10mm and it's too small try an 11mm. But for me it never fails, I spend half my "labor" time looking for the right wrench size. I created this chart and taped one on my toolbox and I have one in my wallet. It reads left to right for sequential fraction sizes.