in Linda Clements' "The Quilter's Bible" she gives the following measurements:
Bed Size ...........Mattress size
Crib.................23" x 46"....(58 cm x 117 cm)
Toddler............30" x 57".....(76 cm x 145 cm)
Twin (single)......39" x 75".....(100 cm x 190 cm)
Full (double).......54" x 75".....(137 cm x 190 cm)
Queen..............60" x 80".....(152 cm x 203 cm)
King.................76" x 80".....(193 cm x 203 cm)
and then you add the drop, pillow tuck, etc.
my "Quit Ref" App for the iPhone gives these measurements:
.............U.S. Mattress.....Comforter.........Bedspread
Crib........27" x 52"...........36" x 60"
Twin.......39" x 75"...........65" x 88"............81" x 110"
Full.........54" x 75"............80" x 88"...........96" x 110"
Queen.....60" x 80"............86" x 93"..........102" x 115"
King.......76" x 80"...........104" x 93"..........120" x 115"
Comforter: (all other than crib size): includes a 13" drop on 3 sides and no pillow tuck
Bedspread: includes a 21" drop (a typical bed height) on 3 sides and a 14" pillow tuck
should help you figure out what you need - always depends on how you want to use the quilt