Paint Calculator
You need your wall area times the number of coats, divided by about 350 square feet per gallon. Enter your wall size, subtract openings, and get the gallons to buy.
How to estimate paint
Add the width of every wall and multiply by the height for the total area, then subtract big doors and windows. Multiply by the number of coats and divide by the coverage on the can — usually around 350 square feet per gallon.
Coats and coverage
Plan on two coats for color changes, new drywall, or strong colors. Primer counts as its own coat. Textured or porous surfaces drink paint, so drop the coverage figure to 300 or less for an honest estimate.
Cost
Multiply gallons by your price per gallon. Quality interior paint runs $30–$60 a gallon. Doing the walls in wallpaper instead? Switch to the wallpaper calculator, or check odd-shaped walls with the square footage calculator.
Frequently asked
How much paint do I need?
Multiply the wall area by the number of coats and divide by the coverage rate — about 350 square feet per gallon. A 360 sq ft wall in two coats needs 3 gallons.
How many square feet does a gallon of paint cover?
A gallon covers roughly 350–400 square feet in one coat on smooth, primed walls. Rough, porous, or unprimed surfaces cover less.
Do I subtract doors and windows?
For a tighter estimate, subtract large openings. Many painters skip small windows because the trim and edges use the extra paint anyway.