Measure once, use the same geometry
Enter each rectangular wall as width, height. Give openings their wall number and coordinates from the left edge and floor. The tool checks that rectangles fit and do not overlap before subtracting their areas for paint. Mixed units are not supported within one plan; the unit selector converts the dimensional fields together.
Two walls, one worked example
A 120 × 96-inch wall and a 144 × 96-inch wall total 176 square feet. A 36 × 80-inch door removes 20 square feet, leaving 156. Two coats at an entered coverage of 350 square feet per US gallon use 0.89 gallon before allowance. With 10% extra, the estimate is 0.98 gallon, rounded to one 1-gallon can.
What measurements cannot decide
Coverage changes with surface, application and product. This planner does not assess substrate condition, concealed utilities or structural safety. Check important dimensions on site and follow the product manufacturer’s instructions. Ceilings and opening reveals are not included.
Questions, answered
Does this include the ceiling?
No. This version estimates rectangular walls only. Primer, ceilings, trim and reveals need separate quantities.