Paint Calculator
Calculate paint quantity, coverage, and costs for interior walls with precision
Calculate Paint Requirements
Room Dimensions
Doors
Standard: 7 feet or 2.1 meters
Standard: 3 feet or 0.9 meters
Enter 0 if no doors on walls
Total Door Area:
21.0 square feet
1 door(s) × 21.0 sq ft each
Windows
Standard: 3 feet or 0.9 meters
Standard: 2 feet or 0.6 meters
Enter 0 if no windows
Total Window Area:
6.0 square feet
1 window(s) × 6.0 sq ft each
Paint Configuration
2 coats typically recommended
Standard: 350-400 sq ft/gallon
Cost Estimation (Optional)
Average: $30-60 per gallon
Example Calculation
Living Room Paint Project Example
Room dimensions: 12 × 14 × 9 feet
Doors: 1 door (7 × 3 feet)
Windows: 2 windows (3 × 2 feet each)
Paint: 2 coats, 350 sq ft/gallon coverage
Calculation Results
Wall area: 2×(12×9) + 2×(14×9) = 468 sq ft
Door area: 1×(7×3) = 21 sq ft
Window area: 2×(3×2) = 12 sq ft
Paintable area: 468 - 21 - 12 = 435 sq ft
Paint needed: (435 × 2) ÷ 350 = 2.5 gallons
Small Room Recommendations
Perfect for bedrooms, bathrooms, or small spaces
Painting Steps
Prepare Room
Remove furniture, cover floors, clean walls
Prime (if needed)
Apply primer for new or dark colors
Cut In Edges
Paint corners and trim with brush
Roll Walls
Apply paint with roller in W pattern
Apply Second Coat
Wait for first coat to dry completely
Professional Tips
Buy 10-15% extra paint for touch-ups and future repairs
Use high-quality brushes and rollers for better coverage
Prime when changing from dark to light colors
Two thin coats are better than one thick coat
Keep a wet edge to avoid lap marks
Understanding Paint Calculations
Wall Area Calculation
Wall Area = 2 × (L × H) + 2 × (W × H)
Where L = Length, W = Width, H = Height
This formula calculates the total area of all four walls in a rectangular room. We then subtract the area of doors and windows to get the paintable area.
Paint Volume Formula
Paint Volume = (Area × Coats) ÷ Coverage
Coverage is typically 350-400 sq ft per gallon
- •Most paints cover 350-400 square feet per gallon
- •Two coats are typically recommended for best results
- •Primer may be needed for new or dramatic color changes
Factors Affecting Paint Usage
Surface Texture
- • Smooth surfaces: Standard coverage
- • Textured surfaces: +10-20% more paint
- • Rough/porous surfaces: +15-30% more paint
Color Changes
- • Similar colors: Standard amount
- • Light to dark: Standard amount
- • Dark to light: +1 primer coat
- • Dramatic changes: +1 primer + extra coat
Pro Tip: Always buy slightly more paint than calculated. Having extra paint ensures color consistency and provides material for future touch-ups.
Important Notes
- • This calculator estimates paint for walls only - ceiling paint is additional
- • Actual paint usage may vary by ±20% based on surface conditions and application method
- • Primer requirements depend on existing wall color and new paint color
- • Professional painters often apply paint slightly thicker, requiring 10-15% more material
- • Always purchase paint from the same batch to ensure color consistency
Paint Types & Finishes Guide
Flat/Matte
Best for low-traffic areas like bedrooms and ceilings. Hides surface imperfections well.
Eggshell
Good balance of durability and appearance. Suitable for living rooms and dining rooms.
Semi-Gloss
Ideal for kitchens, bathrooms, and trim. Easy to clean and moisture resistant.