I need to make a nine patch block that finishes at 6.5 inches. The four corners of the nine patch are half square triangles. What size do I cut the squares and the triangles? Thanks for any help you can give me.

that is an odd size but if you want them to finish at 6.5" then your squares are 2.333" and your half square triangles are 7/8s larger than that, approximately 3.208"

Good luck

Are you sure you need a _finished_ size of 6.5? Or do you need the block to be 6.5 inches before it's sewn into a quilt? The block is always unfinished. It's not finished until it's sewn into a quilt. So a finished block of 6 inches is 6.5 before it's sewn into a quilt. A finished block of 6.5 inches would be 7 inches before it's sewn into a quilt.

If you need a 6 inch finished block it's 6 divided by 3 plus a half inch seam allowance for the squares. Which would be squares of 2.5. For the half square triangles add an inch to the size you need, in this case 2 inches plus an inch, and then square up to 2.5 before you sew into the block.

Cut squares at 7"
I would cut the half square blocks at least 8" and cut down to size. Easier to cut down than to try and be exact. To be exact.....for half squares would be 6.5 plus 7/8"
Too exact for me and too much time so cutting down saves time and is more accurate.

Oh my. I sure mis read that one. I assumed each square finished at 6.5" and not the entire 9 patch.

The nine patch will be at each end of the borders and the borders are 6.5 inches by 60 inches finished.

http://www.quilterscache.com/O/OctagonTileBlock.html
this supposedly finishes at 6 1/2.
or here is a log cabin 7 inches
http://www.quilterscache.com/H/HalfLogSkewBlock.html

Then my math should be correct for you.

Thank you for your help. This will make it a lot easier.