I was taught to use my ruler for measuring and cutting, not the mat. Not to cut on the lines of my mat, so as to not wear it out. I do feel for you. I once measured for blinds, had them made by Three Day Blinds. They were too short and too narrow. I went back to them and they remeasured - they were exactly what I had ordered. Went home and checked the measuring tape I'd used against all the others in the house. It was a bad measuring tape!

Thanks for posting! I never would have thought of that and probably would have been thinking the same things you were - "it must be me; I'm losing it; I give up, etc". I'll keep this in mind now!

I am so happy this topic came up to inform us about the cutting mats may be off. Thanks for the hint to never use them to measure by when cutting. I was constantly having to "clean up blocks" just because of using the mat for measuring . I measured mine and it is off also.

So true about OLFA mats. Used by engineers before we quilters grabbed them

This is just awful for you. I cannot believe it. the time you wasted on this bad product.

really good tip, thank you

i have always used my mat for measuring and have never had a problem , but i dont switch between a ruler and a mat for measurements once i start with the mat i finish the project with the mat

I know this is an older post however I have been so busy over the Christmas period that I am only now catching up.

I never use the measurements on my board when cutting, always use my ruler. My friend who teaches quilting told me when I was first learning that I should always measure with the ruler and to always use the same ruler or set of rulers for measuring and cutting the same project as mixing rulers during a project could also see measurement being off.
Was told that the measurements on the mats are not as accurate as those on the rulers. Have 3 sets of rulers (all different brands) and upon checking the measurements in each of the brands, they are all different, which enforces why I should always use the same set to cut a given project (unless is is a design that doesn't have a set pattern to it) I imagine there is no difference with the mats.

Funny, isn't it -- We always assume the mistake is ours. Glad you figured out it was not your fault.

Most of my cutting mats are Olfas; I do have one June Tailor one for taking along when needed; also have a blue Dritz one. I like the olfas the best; also like the Dritz.