About & methodology

Paint Calculator is a free tool that estimates how much paint a job needs, and what it costs, from the wall area or room size. No sign-up; the math runs in your browser.

How it works

• Wall area = perimeter × ceiling height (or enter it directly).
• Subtract ~21 sq ft per door and ~15 sq ft per window.
• Coverage needed = paintable area × number of coats.
• Gallons = coverage ÷ paint coverage rate (economy 350, standard 375, premium 400 sq ft/gal), rounded up.
• Cost = gallons × a per-gallon price range for the chosen quality.

Important

These are planning estimates. Deep colors, textured or porous surfaces, and bare drywall all reduce coverage and may need primer (a separate product). Buy a little extra for touch-ups.