I was reading another post just now and they mentioned rulers and mats being inaccurate sometimes.
I always measure with my cutting mat. It is the way I learned years ago. I only use my rulers to cut a straight line. I've never noticed any trouble.
Am I in the minority?

I do not use the lines on my cutting mat for measuring.
I use rulers.
Whatever is easier for you I think would be fine.
As a matter of fact, when my mat gets too old, I turn it over on the solid side and use it for a while longer.

i measure with the ruler. i tested my ruler and it is accurate.

I don't use the lines for anything other than lining up my fabric LOL
I tried using them for cutting, and then they didn't measure the same when I switched to my rulers...
But! If it works for you? Go for it :D:D:D

i've used both, if i have to make large cuts i use the lines on the mat for example if i want to cut a yard of fabric, i use the lines on the mat on the ruler is merely a straight edge for the rotary cutter.

I use my rulers to do my measurements when cutting strips and square pieces.

I use only rulers for measuring. I turned my mat over and use the back because I found the lines too confusing when added to the lines on the ruler.

I will use my mat to measure off yards from a bolt. Otherwise, if I'm making something, if I'm measuring wrong on ALL things, then they'll all be wrong together, KWIM? :D

Most of the time I use the rulers but I have been known to use the cutting mat lines. I should probably check and make sure they're in agreement with each other!

I use my ruler most of the time. That being said though if I measure for my borders with the mat then I use the same mat to measure where to cut my border fabric.