Take the binding width you always use, divide by two and add 1/4 inch to each strip.
Example:
If you always use a binding 2.5 inches wide, cut two strips that are 1.25 + .25 =1.5 each
At The Quilt Show Bonnie Browning shows how to do it. It is show 609.
http://www.thequiltshow.com/os/shows.php/episode/609