You do not have to cut it on the bias if you are doing straight edges (most quilt bindings). Obviously if you are doing a scallop, bias is prefered. So the basic calculation is # of inches needed divided by WOF (272 by 31 = 9 strips). # of strips x's width of strips (9 x 2.5 = 23 ") To accommodate seams, I would buy 3/4 yard (actually knowing me, I would buy a yard -LOL).. If you want to do an actual bias, just use the table for 44" wide fabric, fold and cut continuous. This is a whole lot easier than driving yourself crazy trying to figure the correct amount. I would probably add about a 1/3 more of what they asked for because of the difference of 44" wide and 31" wide