The formula for calculating the area of a single-story standard prefabricated house includes the main area of the house plus the area of the canopy. For a double-story standard prefabricated house, the formula involves adding the main area of the house, canopy area, walkway area, and staircase area. Similarly, for a three-story standard prefabricated house, the formula is comparable to the double-story house, with the staircase area calculated as the number of staircases multiplied by 16.06 square meters.