Paint Calculator
Enter the room size and openings to get the paintable wall area and how many gallons to buy.
ft
ft
ft
sq ft
Gallons to buy-
Paintable wall area-
Exact gallons-
Ceiling (if painted)-
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How much paint do I need?
Wall area = perimeter x wall height, minus about 20 sq ft per door and 15 sq ft per window. Most paints cover 350 to 400 square feet per gallon per coat on smooth walls; rough or porous surfaces use more.
Plan on two coats for color changes, and round up to whole gallons so the color stays consistent.
Questions
How much does one gallon of paint cover?
About 350 to 400 square feet per coat on smooth, primed walls. Textured or unprimed surfaces can drop that to 250 to 300.
Do I need two coats of paint?
Usually yes, especially when changing colors. One coat can work for a fresh coat of the same color.
How much paint for a 12 x 12 room?
With 8 ft walls, one door and two windows, about 330 sq ft of wall. Two coats need roughly 2 gallons.