If it's meant to be a sofa throw I like to make them 70 to 80 inches long but no more then 60 inches wide. I figure most people want to be covered with enough quilt so that their feet don't stick out when they move. Most of the quilt I make end up being twin to full size. Once in a while I make a queen size but only when I know who I will be giving it to. Usually then end up being whatever size I have enough material for. I rarely plan, usually go at it with no forethought whatsoever.