Paint Calculator
Calculate exactly how many gallons of paint you need for any room. Account for doors, windows, coats, and waste to avoid overbuying.
How It Works
Understand how paint coverage is calculated and what affects your total.
Wall Area Calculation
Multiply the room perimeter by wall height to get total wall area. Subtract 21 sq ft per standard door and 15 sq ft per standard window for a more accurate estimate of paintable surface area.
Coats & Coverage
One gallon of paint covers approximately 350 sq ft of smooth surface. Most rooms need two coats for even, lasting color. Dark colors or porous surfaces may require three coats for full coverage.
Waste & Buying Tips
Adding a 10-15 percent waste factor accounts for touch-ups, spills, and future repairs. Always buy matching finish (eggshell, satin, flat) from the same batch for color consistency across walls.
Frequently Asked Questions
Common questions about calculating paint needs and coverage.
One gallon of paint typically covers 350 to 400 square feet of smooth surface. For textured walls, coverage drops to 250-300 square feet per gallon. It is always better to buy slightly more paint than needed to account for touch-ups and waste. Most rooms require at least two coats for full coverage.
Two coats of paint is the standard for most interior painting projects. The first coat serves as a primer-like base, while the second coat provides even color depth and durability. Dark or bold colors may require three coats. High-quality paint with good coverage can sometimes cover in one coat over a primed surface.
Yes, paint coverage varies significantly by surface type. Smooth drywall provides the best coverage at 350-400 sq ft per gallon. Textured surfaces like orange peel or knockdown use 20-30 percent more paint. Brick, stucco, and unpainted wood are highly porous and can use up to double the amount of paint compared to smooth surfaces.