Paintable Area = (L × H) − Openings
Paint = (Area × Coats) ÷ Coverage
Total = Paint × (1 + Waste%)
Disclaimer
Results are estimates. Actual paint usage may vary based on surface texture, porosity, and application method. Always purchase slightly more than calculated.
Paint coverage refers to how much surface area a specific quantity of paint can cover. This is typically expressed in square meters per liter (m²/L) for metric units or square feet per gallon (ft²/gal) for imperial units. Understanding coverage is crucial for accurately estimating how much paint you need for your project and avoiding waste or shortages.
Most standard interior latex paints cover approximately 10-12 m² per liter (350-400 ft² per gallon) on smooth, primed surfaces. However, actual coverage can vary significantly based on the paint type, surface condition, application method, and the color being applied. Dark colors over light surfaces or vice versa may require additional coats for proper coverage.
Surface Texture
Rough or textured surfaces absorb more paint than smooth surfaces. Brick, stucco, and textured drywall may require 20-50% more paint than smooth walls.
Surface Porosity
New drywall, bare wood, and unpainted surfaces are more porous and absorb more paint. Using a primer first helps seal the surface and reduces topcoat requirements.
Color Change
Dramatic color changes (light to dark or vice versa) typically require more coats. A tinted primer matching your topcoat color can help reduce the number of finish coats needed.
Application Method
Spray application typically uses 20-30% more paint than brush or roller application due to overspray. Rollers are generally the most efficient method for large, flat surfaces.
- Measure accurately: Take precise measurements of all surfaces to be painted. Include all walls, ceilings, and trim work separately as they may have different coverage rates.
- Account for openings: Subtract door and window areas from your total. A standard door is about 2 m² (21 ft²) and a standard window is about 1.5 m² (15 ft²).
- Plan for multiple coats: Most projects require 2 coats for best results. Factor this into your calculations from the start.
- Add waste allowance: Always add 10-15% extra for waste, touch-ups, and future repairs. Paint from the same batch ensures color consistency.
- Consider surface prep: If using primer, calculate primer requirements separately as coverage rates differ from topcoat paint.