I took the path of least resistance and am cutting everything ever so slightly bigger and then trimming the blocks down.
Thanks goodness the LQS had 40% off their OLFA rulers. I bought a 4 1/2" one and it's been a lifesaver.

Thanks for all the tips

Watson

These guys have given good advice. I struggled with things not fitting even though i.measured the seam allowance. Finally saw the tip about measuring the block after pressing instead of the seam allowance and my units finally fit! It was a Duh moment for sure, but makes sense as your units need to fit together when it's all said and done. I like Presencia 60wt and know where to set my needle for piecing. Much happier camper now that things fit together (most of the time...)

It took me 3 quilts before I got the scant correctly for my machine. Not an issue now because I audition first before I commit to sewing the blocks. Some block patterns I automatically scant stitch now because I have experienced nightmare sewing days. Some blocks I've learned to make bigger and cut to size, which is my preferred method...then you have perfect, smooth pieces. Sometimes I do what Boston1954 does...if all blocks are the same size but not to pattern size, oh well...my quilt is just smaller. Glad something finally worked for you.

Have you checked the measurements of your ruler and your mat? Yes, they can be different! I have one ruler I had to get rid of because the lines were actually off by 1/8”. Use a professional metal tape measurer to check the lines on both. You may be surprised, too...

A really, really easy peasy way to check that seams are indeed 1/4” is to make a trial run with an index card. Those lines are 1/4” apart. It works and doesn’t take very long to figure out how to adjust the needle or whatever. Thread thickness does matter, BTW.

if you are using unwashed fabric and then using steam to press the sewn units, that might be one place where you might be getting " off".

i had a 5-inch square shrink to a 4.5 x 5 square once. i washed some hoffman strips that were 2-1/2 before washing and they were 2-3/8 wide after washing.

Yes, that was what I was about to mention. The measurements between rulers can be different between manufacturers too. The longer the measurement, the worse the problem if using different rulers.

Also, some of the lines on rulers are thicker than others making it hard to be consistent. I find that the Quilters Select rulers have nice thin lines that are easier to see and a grippy back that makes cutting fabric easier. I'm treating myself to one new one a year when they are on sale.

I have found most of my size problems are my cutting. That's why I bought an Accuquilt. I'm really happy with it so far.

I love the stripology ruler by creative grids.

I don't worry about it, I'm with Boston, my points are usually NOT cut off, so I'm okay with a "slightly" off measurement. There's simply more to life than worrying about if your block is exactly as it's supposed to be.

Even the manufacturer's of rulers/mats say don't use the lines as "measurements" and if you start with one brand of ruler on a quilt, stay with that brand for the entire quilt, so why are we expected to be absolutely perfect?