Home improvement
Paint Calculator
Work out how many gallons of paint a room needs, including coats and primer.
Result
Coverage varies with surface texture and colour change. Rough or previously unpainted surfaces can drop coverage by a third, and a dramatic colour change usually needs primer plus two coats.
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About this calculator
How much does a gallon of paint cover?
Around 350–400 square feet on smooth, previously painted walls. Textured, porous or bare surfaces absorb considerably more.
Do I need primer?
Yes for bare drywall, stained areas, or a big colour change. Particularly going light over dark. Primer is cheaper than a third finish coat.
Should I deduct doors and windows?
Deduct large openings, but leave small ones in. The extra paint covers cutting in, touch-ups and the inevitable second trip up the ladder.
The formula
gallons = (paintable area × coats) ÷ coverage per gallon
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