Skippy (my 4 pound male Yorkie) comes back from the groomer with a triangle-shaped bandana 10 1/4 to 10 1/2 inches on the short side of the triangle. A quilter would cut a 10 1/2 inch square and then cut the square on the diagonal. Since most of the fabrics are 45 inches wide, the groomer probably cuts strips across the grain of fabric 10 1/2 inches wide and then cuts those strips into four squares...then the diagonal of each square. They also have been cut with pinking shears to keep them from raveling...not sure if you can do that with your material. As a quilter I would also highly recommend a rotary cutter, board and large plastic quilting ruler. You can buy all of them in the sewing department of WalMart (or a similar store...they are very common.)

Tiffy, my female Yorkie, doesn't wear a bandana. She gets a bow in her hair.