a queen bed is 80 x 60.
if you like a 15" drop and no pillow wrap then it should be
80 + 15 = 95" (at the foot only)
60 + 15 + 15 = 90" (because there are two drops).
remember that today's mattresses and boxsprings are higher than most instructions call for.
i personally like 96" square. don't as why. i think the squares are easier to plan. if you like to wrap the pillows, add another 10" to the length for the undertuck and the headboard tuck..,
or 7" to just drape it on top.
i hope this helps you.