Help determining correct scale measurements.?

I have a 30" L x 22" H sheet of paper which i plan to paint a U.S. flag on for the 4th of July. There are 13 horizontal stripes, and a blue "Union" square which, according to U.S. regulations, takes up approximately 40% and is located in the top left hand corner. I need help properly scaling the flag so that I can paint 13 equal stripes on the flag and the Union.