Paint coverage formula
paint = ((wall length × height) − openings) × coats ÷ coverageThe result shows exact calculated volume and rounds one-gallon cans up for a practical purchase count.
Wall paint calculator
Use the combined length of the walls, subtract doors and windows, and account for every finish coat.
Enter wall and paint details
Add the lengths of every wall receiving the same paint.
Coverage depends on both paint and substrate
A label's coverage range assumes particular application conditions. New drywall, porous masonry, strong color changes, textured walls, and spray application can consume more material than a smooth sealed wall.
- Calculate primer separately when the system requires it.
- Use net wall area after openings and the actual number of coats.
- Keep enough matching paint for touch-up and record the product and tint formula.
Coverage is not universal
Porous drywall, masonry, dramatic color changes, spraying, and textured surfaces can reduce coverage. Use the label for the paint and surface you are actually using.
What this estimate excludes
This calculator covers wall finish coats only. Estimate primer, ceilings, doors, cabinets, and trim separately. Confirm preparation, ventilation, drying conditions, protective equipment, and coating compatibility before work begins.