I only use my mats for lining up, never for marking.

I, like the others use the lines on the ruler. I also would cut even in squares, like cut to 9", in this case and trim down. You will never miss an 1/8" of fabric.

Don't use your mat for measuring, use your ruler. The lines on the mat are used for lining up the fabric. That one opinion.

I agree with Tartan...use your ruler for measuring to be more accurate and over cut and then trim to correct size. Everyone sews their 1/4" seam just a bit different so if you over cut you will still have the correct size block.

I will use my cutting mat for measuring "big" pieces of fabric for things like pillow cases and recyclable-like bags.

1/8 is half of 1/4, so you could eyeball it and cut between 8 3/4 and 9. But I agree with the others, it's better to cut to 9 and trim.

I'm with Peckish. Don't over-complicate.

It really irritates me when Jenny fromMSQC uses her mat to measure....kind of blows "our" rule of using rulers to measure out of the water!

I checked my mats against my rulers - or my rulers against my mats - they are "close enough" for "big" cutting.

I also use the ruler and not the mat for measuring and cutting.

Once you find the right measurement, why not put a strip of blue painter's tape at that mark so you won't have to keep searching for the right mark each time. I find this very helpful in cutting those fussy increments.