Okay,I sold waterbeds and regular mattresses for over 20 years so I can tell you the sizes of mattresses,but only across the top as many mattresses are of different thicknesses. The standard depth or thickness is 7" to 9". Twin= 39"x 75", Full/double=54"x75", Queen=60"x 80", King=76"x80", California K/Q mattress only is 60"x84 and 72"x84. I imagine if you measure from the top of the mattress towards the floor how long you want the quilt to hang and double it for width, then do the same amount to the bottom for length you will have the hang you're looking for. The measurements for a K/Q comforter are I believe 96"x 108".