It depends on how the quilt is going to fit. A regular twin size mattress is about 34 X 75 inches. If you want a nice hang over, I usually go 54 X 90. I would figure out how fabric to do the top in 1 fabric and then divide by 2 and then add an equal amount of the second colour. This is just a general guideline because it depends on which Chevron pattern you use. Some are made with rectangles or some with triangles.