Block Size
 

I'm confused that a 9" block size finished would start as a 9.5" block with seams.
Don't you sew a 1/4" seam on all 4 sides to connect the blocks in rows?
Wouldn't that add an inch to the 9" block before it is sewn on all 4 sides?

It used to be that you had to add seam allowances to quilt patterns. Now, I rarely see a quilt pattern that you need to do this. If your pattern is pre 1990, I would check to see if the original required the addition of seam allowances. If it is a more modern pattern, the seam allowances have been included and stitching your block with a quarter inch seam will result in the correct finished size.

Ummm....NO!! If you look at a SQUARE that is 9" on each side. Now add 1/4 inch on EACH SIDE. That makes a 9 1/2" square. You forgot that the square has a top and bottom which are different from the left and right sides.

And when in doubt, get out your graph paper and draw it, then measure it. Sometimes that helps me visualize what the pattern wants.

A 9" finished block is a 9" square, or 9"x9". So it starts out as 9½"x9½". So, yes, you've added a quarter inch to each side, but it's measured as a half inch to the width (the sides) and a half inch to the length (top and bottom). Were you thinking it should start out as 10" instead of 9½"?

Block Size
 

Yes, I was thinking that if you added a 1/4" seam to all sides of a 9" block it would make it a 10" block you would have to cut in order to sew it on all 4 sides with a 1/4" seam to get a 9" finished block in the quilt.
1/4" added to each side x 4 sides would equal 1" more.

GingerK has an excellent explanation a few posts before this one. You must add ONLY 1/2" to get the desired size. Please take the time to draw a visual if you still have your doubts.

Thanks, I think I got it.