Paint Calculator
Calculate how many gallons of paint you need for walls, ceiling, and trim.
Room Dimensions
Openings to Subtract
Each door ~20 sq ft
Each window ~15 sq ft
What Are You Painting?
Results
Total Gallons Needed
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Quarts (if buying small)
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Total Wall Area
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net paintable area
Based on standard coverage of 350 sq ft per gallon. Dark colors, rough surfaces, or bare drywall may require more. Always buy 10-15% extra for touch-ups.
How Much Paint Do You Need?
Standard interior paint covers approximately 350-400 square feet per gallon with a single coat. To calculate the amount needed, find the total paintable wall area, subtract windows and doors, multiply by the number of coats, then divide by 350 to get gallons.
Wall Area = Perimeter x Height - (Doors x 20) - (Windows x 15)
Gallons = (Wall Area x Coats) / 350
Gallons = (Wall Area x Coats) / 350
For ceilings, calculate length x width and divide by 350. Always round up to the nearest quart or gallon when purchasing, and buy a little extra for future touch-ups — paint color lots can vary between batches.