(2 times the finished binding width + Seam allowance) X 2 this is what I found on about.com. Is this the formula that you use for double fold binding.The question came about because I decided that my flip flop quilt for the school need a wider binding, I usually do 1/4 binding. My searches on here came up empty and online it came up book binding or snowboard binding or a calculator to figure how much , but not starting width=finished binding size. I fiqure someone on here knows the answer :-D Thanks Daphne