I always use double straight fold binding. Having no raw edge to deal with is why I use it. Some of my wide bindings mean cutting a strip 4 1/2 " wide.

For double fold binding, I use finished width times 6 plus 1/8 inch. So 0.75*6 + 1/8 = 4-5/8 (width to cut the strips). Or your way works if I don't put the raw edge of the binding all the way to the edge of quilt/backing, but then I am worried that the binding will not be "full" as the seam allowance will be several layers thicker than the final folded edge of the bound quilt.