Here is a method of cutting half square triangles perfect everytime and a way to make 8 at once.
Using this technique minimizes waste and ensures accuracy when you’re cutting a large number of identical squares.
Place a layered pair of squares (right side together) on a grid that works best for you. On the wrong side of the fabric, use a pencil to mark horizontal, vertical and diagonal lines. Diagram 1
Sew layered square together with four seams, stitching 1/4″ on each side of drawn diagonal lines. Cut on drawn lines to make eight triangle-square units. Diagram 2
Math Made Easy!
(Use the same size squares to make multiple triangle-squares)
To determin what size squares you need to cut, multiply the desired finished size of the trainagle-square by two, then add 1 3/4″. For example, for a finished triangle-square that is 2 1/2″ square, use 6 3/4″ square.
2 x 2 1/2″ (finished size) = 5″ 5″+ 1 3/4″ = 6 3/4″