How much paint for a 18×18 room with 9' ceilings?
Answer
4 gallons (2 coats)
Total wall area: 648 sq ftPaintable area (after openings): 551 sq ftCoverage needed (2 coats): 1,102 sq ft
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How We Calculated This
Gallons = (Paintable Wall Area × Coats) / 350 sq ft per gallon
Walls: 2 × (18 + 18) × 9 = 648 sq ft. After 15% openings: 551 sq ft. × 2 coats = 1102 sq ft ÷ 350 = 4 gallons
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Calculated using verified formulas. Last updated March 2026.