Originally Posted by QuiltnNan

or, being a math major, the square of the hypotenuse equals the sum of the squares of the other two sides. 10.5 squared plus 10.5 squared = 220.5. the sq root of that is 14.849". i would round that up and add the seam allowances. thus, a 15.5" square can be cut diagonally to fit in the spot.