How much paint for a 18×18 room with 12' ceilings?
Answer
5 gallons (2 coats)
Total wall area: 864 sq ftPaintable area (after openings): 734 sq ftCoverage needed (2 coats): 1,469 sq ft
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How We Calculated This
Gallons = (Paintable Wall Area × Coats) / 350 sq ft per gallon
Walls: 2 × (18 + 18) × 12 = 864 sq ft. After 15% openings: 734 sq ft. × 2 coats = 1469 sq ft ÷ 350 = 5 gallons
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Calculated using verified formulas. Last updated March 2026.