Hi, I am fairly new to the board, however, at our local quilt guild they taught us not to pay attention to the measurements on our cutting mat because they are not always accurate. They taught us that if the measurement on the mat is off by only 1/16", the quilt block will be off because you are multiplying that 1/16" by each piece you cut. Soon you could be off by 1/4" or more. They said to pay attention to the measurement on your cutting ruler. Does this make sense? I have found it to be much more accurate. Hope this helps you.