How much paint do I need?
Paint = wall area × number of coats / coverage per gallon (or liter)
- Work out the area: the room's perimeter × wall height, minus doors and windows. If you paint the ceiling, add length × width.
- Choose the coats: almost always two. One coat is only enough when repainting the same color over walls in good condition; three when covering a dark color with a light one.
- Divide by the coverage printed on the can and round up.
Example · a 12 × 12 ft bedroom with 8 ft ceilings
Perimeter 48 ft × 8 ft = 384 sq ft, minus 35 sq ft for a door and a window = 349 sq ft. Two coats at 350 sq ft per gallon: 349 × 2 / 350 ≈ 2 gallons. Add 1 more gallon if you also paint the 144 sq ft ceiling.
Frequently asked questions
Do I need primer?
On new drywall, stained walls or when going from a very dark color to a light one, yes: a coat of primer saves paint and gives a more even finish. Paint-and-primer products can replace it on walls in good condition.
How much is a gallon in liters?
A US gallon is 3.785 liters; a quart is a quarter of a gallon (0.946 L). Switch the units above to work in meters and liters.
And for tiling?
Work out tiles, boxes, thinset and grout with the tile calculator.