??? sizes for square in a square in a square
 

I'm sure this has been addressed many times, but I did not need it until now and do not know how to find the answer on the previous boards. I am making a storm at sea and need to know how to figure the sizes for a square in a square in a square for the center block and a square in a square for the corner. The final block is 12 inches, but the center is 8" with 1/2 inch seam allowance and the corner is a 4 " square adding 1/2 inch for seams. If this is something someone could help me find, it would be appreciated. Thanks.

I would draw it on graph paper and measure each section.

Here's one:
http://www.quiltersparadiseesc.com/C...Calculator.php

If that one doesn't work (or make sense) just google 'square in square calculator' there are several others that come up.

Nice tool -- thanks for posting the link!

Is this what you need?