How much drop do you want on the sides of the quilt when it's on the bed? A queen mattress is 60"x80" so you already have a 14" drop on each side. Decide what you want for a finished size and add border width to get to that size. Borders are not mandatory, nor do they have to be the same width on all four sidess. The top and bottom borders can be wider than the sides and still look great.