Binding length and fabric for the edge of your quilt.
Includes ~10\u2033 for corners and join. Strips cut on grain across a 40\u2033 usable width.
Binding finishes the edge of a quilt. The length you need is the perimeter of the quilt, which is two times the width plus two times the height, with about ten inches added for the corners and the joins. For a 60 by 80 inch quilt, that is 280 inches plus 10, or 290 inches.
Divide that length by the usable width of the fabric, about 40 inches after trimming the selvages, to find how many strips you need, then round up. Seven and a quarter strips means eight strips of 2.5 inches, which is 20 inches of fabric, so about five eighths of a yard is enough.
Strip widths of 2.25 to 2.5 inches are common for double fold binding, and wider strips are used for thick batting. Join the strips with diagonal seams, press the seams open, and fold the strip in half along its length before sewing.
Cut a little extra, since a miscalculation is awkward to fix after the quilting is done. Bias binding is better for curved edges, but straight grain is fine for most quilts with square corners.