Quilt sizes vary. With the depth of mattress' there is 'no set sizes'. I made a quilt for DD's king size with a 18" deep mattress, my queen is 15".
The quilt I just finished for me, I measured down the sides to where I wanted (approx.) the quilt to hang, plus the size of the mattress.
Mattress Sizes
Crib Mattress Size: 28" x 52"
Twin Mattress Size (Single): 39" x 75"
Full Mattress Size (Double): 54" x 75"
Long Twin Mattress Size: 36" x 80"
* Most beds in college dorms have long twin mattresses
Queen Mattress Size: 60" x 80"
King Mattress: 76" x 80"
California King Mattress Size: 72" x 84"