Free Paint Calculator — All Cities

Paint calculation is deceptively tricky. You need wall area (perimeter times height), minus doors and windows, times the number of coats, divided by coverage per gallon — which varies based on surface texture, paint quality, and application method. Getting it wrong means either leftover custom-tinted paint you cannot return, or a mid-project store run hoping the remix matches your dye lot.

Interior wall paint covers approximately 350 sq ft per gallon on smooth surfaces, dropping to 280–300 sq ft on textured walls. Exterior paint covers about 300 sq ft per gallon due to rougher surfaces. Primer covers 300 sq ft per gallon. Two coats is the standard for any color change — one coat only works for same-color refreshes or when using paint-and-primer products.

Pricing spans a wide range: basic flat paint (Glidden, ColorPlace) runs $22 per gallon, mid-range eggshell (Behr, PPG) averages $45, and premium paint (Benjamin Moore Regal, Farrow & Ball) reaches $85 per gallon. The actual cost difference per room is often under $50 between budget and premium — making premium paint one of the best value upgrades in home renovation.