Most bunks are the same size as what they call a college size twin. The matress is longer then a standard twin. I would make the quilt 75" wide by 100" if he likes to fold over the quilt when he makes the bed. This is the size my hubby had me make for him. He is 5'5 and 145 lbs, , but would accomadate me also if I was on the truck. Tho I would prefer 80" wide , cause we steal covers from each other.