I had a top that was a mass of bias edges. No amount of measuring was going to give me a true length for my border. I finally did the math--finished size of block x number of blocks + 1/2 inch and marked every intersection on my border fabric. I made sure that everything was pinned to match up with the markings and sewed with the body on the bottom so that my feed dogs would help gather in any bias stretch. It worked like a charm!! And this is my go-to method for any borders.