The accuracy is excellent. Tread depth is measured in mm, thousandths of an inch and fractions of an inch. The one thing that could be improved, is the fractions of an inch. For example, it gives you 1/4", 1/8", 1/16", 1/32", 1/64", 1/128" The only fraction of an inch that is useful to me in automotive tire application is 32nds. The rest is very distracting and hard to remember. MM's are easy to use as they are progressive, I just have never used them. Thousandths of an inch is very helpful in metal working, I'm not sure if I would use this setting. Perhaps I can adapt to the different ways of measuring tread depth, because it's a remarkable tool.