If you set quilting blocks on point, here is an easy guide to Corner Setting Triangles

Parent Squares for Common Quilt Block Sizes

4-inch blocks: cut 3 3/4-inch parent squares

6-inch blocks: cut 5 1/8-inch parent squares

9-inch blocks: cut 7 1/4-inch parent squares

10-inch blocks: cut 8-inch parent squares

12-inch blocks: cut 9 3/8-inch parent squares

14-inch blocks: cut 10 3/4-inch parent squares

15-inch blocks: cut 11 1/2-inch parent squares

Examples of onpoint quilts using Corner Setting Triangles by Donna Jordan

Click on the image for the free pattern download from Jordan Fabrics