Paint Calculator

Calculate how many gallons of paint you need for a room. Accounts for doors, windows, and multiple coats.

This calculator figures out how many gallons of paint a room needs and what that will cost, based on wall area, coats, and openings. Number of Coats has a direct, proportional effect on Exact Gallons -- two coats use exactly twice the paint of one coat, since the calculator multiplies the paintable wall area by the coat count before dividing by paint's standard coverage rate of 350 sq ft per gallon (Gallons Needed then rounds that exact figure up to the next whole can). Wall Height also drives Total Wall Area directly: taller walls mean more area to cover for the same room footprint. Doors & Windows reduces Paintable Area but never touches Total Wall Area itself -- the calculator assumes about 20 sq ft of unpaintable surface per door or window and subtracts that from the wall total only after the total is already computed, which is why the two outputs can diverge noticeably in rooms with lots of openings. Cost Per Gallon scales Estimated Cost directly and defaults to $40 but is meant to be overridden with your actual paint's price. This estimate assumes a single, uniform coverage rate for all paint types and doesn't account for texture, primer needs on new drywall, or ceiling area, which would need to be calculated separately.