Paint Calculator

Find how many gallons of paint and primer a room needs, based on its size, doors and windows, and how many coats you plan.

Ceiling
21 sq. ft. each.
15 sq. ft. each.
Sherwin-Williams says 350 to 400; check the can.
Primer
Primer covers about 200 to 300 sq. ft. per gallon; figured at 250.
$
Fractions and decimals both work.
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Gallons
Area to paint
Paint needed
Buy
Primer
Cost

Room List

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RoomAreaCoatsPaintPrimerCostRemove

How Much Paint Do You Need?

Find the area you're painting: the room's perimeter times the wall height, less doors and windows, plus the ceiling if it's getting the same paint. Multiply by the number of coats and divide by the coverage on the can.

Wall area = 2 × (length + width) × height − doors − windows
Gallons = area × coats ÷ coverage per gallon

Sherwin-Williams says a gallon of paint typically covers 350 to 400 square feet, and a gallon of primer 200 to 300. Rough, porous or dark surfaces take more.

Worked Example

Gallons for Common Rooms

Two coats on walls with 8′ ceilings, one door and two windows, at 350 sq. ft. per gallon.

RoomWall AreaGallons

Tips

Buy by the gallon when you need more than about half a gallon; quarts cost much more per ounce. Keep a little extra from the same batch for touch-ups. Prime new drywall, stains and big color changes. Ceilings and trim usually take different paint, so figure them separately.