quiltsfor

To compare it with other Mattress sizes if that helps:

Popular Mattress Sizes

• King Mattress Size: 76” X 80”
• California King Mattress Size: 72” X 84”
• Queen Mattress Size: 60” X 80”
• Full Mattress Size: 54” X 75”
• Twin XL Mattress Size: 38” X 80”
• Twin Mattress Size: 38” X 75”

So since a XL Twin mattress is as long as a Queen size mattress, make the quilt the width of a twin quilt and the length of a Queen quilt, unless more overhang or pillow tuck is wanted.