To estimate paint quantity for your house exterior, consider its size, number of stories, and desired number of coats. The coverage rate of the paint you choose also influences the amount needed. Generally, for a single-story house around 1,500 square feet, you will need approximately 5-7 gallons of paint for two coats, assuming a coverage rate of 350-400 square feet per gallon. For larger houses or multiple stories, adjust the quantity accordingly. Remember to account for any trim, shutters, or other details that may require additional paint.