Cutting mats
I use the cutting mat to measure, but I don't use any other method. If it is off, it is off all the way around. I have seen many rulers that are 'off' over the years. If you only use that one, you are OK. I make wine, and the buckets for fermenting wine are all over the place. One of the first things they tell you to do is use your tried and true gallon container and fill the bucket with that. If you correct the marks along the way, you are in good shape. I think the problem with measures is that these things are made in countries that use the metric system, and changing to 'American' measures is a guess.
Phyllis