Paint Calculator
Calculate gallons of paint for walls and ceilings by room dimensions.
Results
Paintable Area —
Gallons Needed —
Based on 350 sq ft coverage per gallon. Textured walls or porous surfaces may require more paint.
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How to Calculate Paint
One gallon of paint covers approximately 350-400 square feet of smooth wall surface. To calculate how many gallons you need, find the total wall area and subtract openings.
Paint Formula
Wall Area = Perimeter × Height
Subtract: Doors (21 sq ft each) + Windows (15 sq ft each)
Gallons = (Paintable Area × Coats) / 350
Subtract: Doors (21 sq ft each) + Windows (15 sq ft each)
Gallons = (Paintable Area × Coats) / 350
Coverage Rates
- Flat/matte paint: 350-400 sq ft per gallon
- Eggshell/satin: 350 sq ft per gallon
- Semi-gloss: 350 sq ft per gallon
- Primer: 200-300 sq ft per gallon (more porous)
When to Use Extra Coats
- 1 coat: Touching up the same color, or using paint + primer over existing light color
- 2 coats: Standard for most repaints and color changes
- 3 coats: Going from dark to light, painting over stains, deep reds or yellows
Tips for Buying Paint
- Always round up to the nearest gallon — leftover paint is good for touch-ups
- Buy all paint at once to ensure consistent color (same batch/lot)
- Textured walls use 20-30% more paint than smooth walls
- Standard door size is 3' × 7' (21 sq ft); standard window is 3' × 5' (15 sq ft)
- For large rooms, a paint sprayer can cut application time in half compared to brushing
- A quality paint roller kit gives a smooth, even finish on walls and ceilings