The binding for quilts or quilted projects can be cut on the straight grain of the fabric, or on the bias. Bias is fabric which is cut on a 45 degree angle to the woven, selvage edge. This makes the strip more flexible which is important for curved edges. Double-fold bias binding is most commonly used. To make bias strips, first cut a small nick on the selvage edge of the top of the fabric. Tear down the complete length of each side, pulling quickly so you don't distort the shape. This will show you the true grain of the fabric.
Fold down one corner until it meets the bottom edge of your fabric piece.
Cut down the fold. The bias, which is the edges running at a 45 degree, where the fold was, will now be exposed. Move the small piece of fabric to the opposite side of the larger piece.
Place the small piece of fabric over the larger piece. Pin and sew with right sides together, using a 1/4" seam. Press seams open.
Turn the fabric over and cut the strips from a straight edge to the opposite straight edge. Cut your binding strips 6 times the width of the desired finish.
A 1-7/8" wide stripe will finish at 1/4" wide, 2- 2-1/2" will finish at 3/8" wide and, 3-1/4"will finish at 1/ 2" wide. I usually cut 2-1/2" wide strips.
Sew the strips together, end to end using 1/4" diagonal seams, to create a continuous length. There should be the length of all sides of the quilt plus several inches. Press the seams open and trim off any flaps. Fold this continuous strip in half, wrong sides together, down it's length. Press. You now have a strip of double-fold bias binding. Binding cut across the grain would created in the same way.