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1. Work backwards. You want a finished 12" block. You're sewing 4 equal size patches together to make it. That means each of those patches needs to be 6" finished, which means they are 6.5" unfinished. Now if those 4 patches were part of one big block (the 9-patch) then the 9-patch would have been 13" unfinished, or 12.5" finished. That means each patch in the 9-patch is 12.5"/3 finished = 4 1/6" (4.166666") finished, or 4 2/3" (4.666666") unfinished. Your strips need to be 4 2/3" wide.

Now to check the answer: Take 4 2/3" wide patches, sew into a 9-patch, you lose 1" with two seams so you have an unfinished block that is 3*(4 2/3) - 1" = 13". Cut into 4 pieces to get 4 patches that are 6.5" unfinished, this time you lose only 1/2" when you sew them together, so the resulting D9P (unfinished) is (2*6.5) -.5 = 12.5"

2. Originally Posted by quiltingnonie
I want to make a D9P block that will be 12 1/2" (12" finished)
When I cut the squares @ 4 1/2" and sewed them back together, cut them in half, it ended up being too small. So I tried 4 3/4", and couldn't get that to work either. :cry:

What am I doing wrong?

3. Because my brain can only cut accurately in increments of 1/4", I think I will just use the 4 3/4" original block cut and then trim the final block down. Hope it doesn't look too weird :roll:

Thanks to all you mathematical wizzards - I admire your thought processes :thumbup:

4. Oh brother, I hate math :lol:

5. Originally Posted by quiltingnonie
I want to make a D9P block that will be 12 1/2" (12" finished)
When I cut the squares @ 4 1/2" and sewed them back together, cut them in half, it ended up being too small. So I tried 4 3/4", and couldn't get that to work either. :cry:

What am I doing wrong?
Maybe this will help: (Cookie Cutter aka. D9P)