You should cut your strips 8 1/2" long, not 8".

Finished seams...strips will measure 2 1/4 + 2 + 2 + 2 1/4 = 8 1/2. So if you cut the stirps 8 1/2 long it will fit together perfectly.

They both should be 8.5"x8.5", not 8x8"...are they?

Your forgot to add the seam allowance. You need to cut the strips 8.5" long, not 8 if you've already cut them all and want to salvage them, just cut a half inch from the red or striped fabric. Cut the same one on all the blocks. One rail will be a bit narrower, but that will just add interest to your quilt.

like the colors

wish i could help you with the math, i usually learn by trial and error, however, the fabrics are gorgeous together. can't wait to see the finished quilt. please share when you finish. :)

Hope your question has been answered. I just want to say that I like the fabrics you have chosen. It will be pretty when you finish.

Whenever I have that problem it's usually because I didn't sew accurate 1/4" seams in all the pieces. I've found I do a lot better when I use my 1/4" seam foot, rather than the regular sewing foot.

We have all been in your shoes. If you have already cut most of the fabric fine. It will be a little smaller block is all, so cut the block that is to big to match the smaller one. You have not ruined anything. We all learn something new in quilting each day. Even us old folks learn new things and make mistakes.
Keep on Sewing!!!!!!!

did you cut them 8 1/2 " long?

Thanks. I watched a tutorial on Missouristarquilt and when she sewed her jelly roll strips together using a 1/4 in seam the instruction was to measure from top to bottom which was said to be 8 inches and then cut in by that amt to make a perfect sq. so that is what I was following. I only cut these two so far so I should be able good to go from here. Thanks again and again as always.