Help please with measurements
 

I would like to make a d9p which finishes at 12 1/2 inches square. I know if I use 4 1/2 squares I will end up with a 12 1/2 inch nine patch, but I will have to cut it in two directions to make the d9p. Anyone know what size squares I need to start with to end up at 12 1/2 inches square?
Thanks for any help you can give me.

This may help. It was posted by another poster a few days ago:

I'm not where I can measure but I think that's about the size I got when I used 5 inch squares.

Edit: Looks like someone else beat me to it with a very nice chart. :)

If you look at the chart none of the D9P blocks actually come out 12.5 inches. You can do a 9 patch that size but not a D9P.

You only lose 1/2 inch when going from the 9p to the d9p, because you're just slicing and then making one 1/4" seam, which removes 1/4" from each piece.

Yes, which means for a block to end up 12.5 it would have to be 13 inches before you cut it. 13 does not divide evenly by 3.

If you really need a 12.5" finished d9p block, you can cut your original patches at 4 5/6" (difficult to measure with standard quilting tools) or you could cut them at 5" and then trim down the finished d9p block. Because of the geometry of the block, the finished quilt would still look like a d9P.

??? I'm not sure what my statement has to do with yours ???

You could always trim the 13 inch block that you get using 5 inch squares down to 12-1/2 inches, taking the same amount off all four sides.

Thanks for all your help.