Sixteenth
Paint Calculator
Enter the room size, doors and windows. You get the wall and ceiling area and how many gallons to buy for the number of coats.
Doors count as 21 ft² and windows as 15 ft². Coverage is printed on the can, usually 350–400 ft².
How much paint for a room
walls = 2 × (length + width) × height − 21 × doors − 15 × windows
gallons = area × coats ÷ coverage
Rough, porous or dark surfaces take more paint than the label says, so use the low end of the coverage range for textured walls, new drywall or a big color change. Prime new drywall and patches first.
Questions
How much paint do I need for a room?
Wall area = 2 × (length + width) × height. Take off about 21 ft² per door and 15 ft² per window, multiply by the number of coats, and divide by the coverage on the can, usually 350–400 ft² per gallon.
How many coats of paint?
Two coats is standard. One coat can be enough when you repaint the same color, and new drywall needs primer first.
Is a 5-gallon bucket cheaper?
Usually. The calculator rounds up to whole gallons and suggests 5-gallon buckets first, then single gallons.