Why don't my 2,1/2 inch squares measure 2" when finished?

I've been meaning to tell you all to invest in the "Shape Cut Plus" by June Tailor. I got mine with a 50% off coupon at Joann Fabrics. If you don't have one it's worth every penny!!! It is excellent for cutting strips with super accuracy very quickly. I am so impressed with the improvement it has made for cutting out my strips.

Coffeebreak, try sewing with the scant 1/4" seam and see if that solves the problem. Do you have a machine that will allow you to change your stitch width? Also, are you using a 1/4" quilting foot? The steam shouldn't be the problem. I use steam all the time and most of my fabrics are not pre-washed. Make sure after ironing the back of the block you also iron it on the front.

Have you measured your seams? I used to have that problem as well until I really and truly found where my 1/4" is on my machine regardless of the markings. Now my blocks are the size they should be. I don't have much squaring up anymore.

Another thought is when cutting...where on the ruler do you line up your fabric? Is it to the left of the marked line or the right or in the center? That too, makes a big difference when cutting. I found on my rulers I use the left of the line and get a good true measured 2 1/2" if that's what I am cutting. Otherwise, just being off the thickness of the cutting line will add up. As long as you are consistant where you cut, your blocks should all be the same size in relation to your strip size.

I always sew a "scant" 1/4" seam to help the blocks come out to the right size. This really helps. So if your measurements are correct and your seams are correct, the issue must be "losing" part of the block as the fabric lays over the seam.

Don't get too frustrated--we all struggle with these issues. As time goes on you'll learn your own techniques to make a "perfect" block. And, here's a hint--Fons and Porter never show us their measurements! Their blocks can be slightly small as well!

I have gotten a new machine and was having the same problem. I use a foot with a guide, so I moved the needle position to the right a few times and then could get a nice and easy scant 1/4 inch.

Does your needle move back and forth when you change stitch type? I have three different straight stitches on my machine. Depending on which one I use depends on which side the needle moves. It goes from side to side and can vary your stitches up to a quarter of an inch. When you mark your 1/4" on your machine make sure you are using the same needle setting every time or it will throw your seam out.
I found this out the hard way and lost some points on a star quilt I made.

I always use a 1/4" foot when piecing and always have to move my needle position to the right a bit with my Janome and Bernina to get a scant 1/4" seam. I was told in a class once that when tutorials, instructors, and/or printed instructions say 1/4" seam, in quilting that is always a "scant" 1/4" seam -- people/instructions just don't always include the word "scant".