Paint & Primer Estimator

Estimating interior wall paint accurately prevents frustrating mid-project supply runs and minimizes leftover cans of custom-tinted paint. Decorators and homeowners need to know how many gallons or liters of paint to purchase based on room dimensions, openings, and desired coat coverage. Providing the room length, width, ceiling height, total number of standard doors and windows, and number of intended coats produces the gross wall area, net paintable surface, and rounded paint quantity.

Reading the output gives you both the net wall area and the total cumulative surface to be coated across multiple applications. The baseline coverage calculation utilizes the industry standard spread rate of three hundred fifty square feet per gallon of architectural latex paint. Keep in mind that porous drywall surfaces, unprimed textured plaster, and drastic color transitions require significantly more paint or an initial dedicated primer coat to achieve complete visual opacity.

Gross wall area is calculated by multiplying room perimeter by ceiling height, from which standard door and window surface areas are subtracted to find net paintable area. Net area is multiplied by the chosen number of coats and divided by the standard spread rate of three hundred fifty square feet per gallon. The result is rounded up to the nearest whole gallon and converted to equivalent metric liters.