With sun angles in the Northern Hemisphere, the awning height should cover 65%-75% of the window height on the east or west side of the house. On the south side, only 45%-60% of the window height needs to be covered.
The recommended awning projection is 50% of the window height. Be sure the awning does not protrude into the path of foot traffic, unless it is at least 6 feet 8 inches above the ground.
The awning should generally be 12 to 24 inches wider than the window.