Paint Calculator
Find out how many gallons of paint and primer you need for a room.
| Item | Amount |
|---|---|
| Walls | |
| Ceiling | |
| Primer | |
| Estimated paint cost |
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How the paint calculator works
The wall area is the room's perimeter times its height. The calculator subtracts 20 sq ft for each door and 10 sq ft for each window, multiplies by your number of coats, and divides by how far a gallon goes. The ceiling is length times width. Everything is rounded up to whole gallons, since you cannot buy part of a can. Primer is figured at about 250 sq ft per gallon.
Worked example: a 12 ft x 14 ft room with 8 ft walls
The walls are 416 sq ft. One door and two windows take out 40 sq ft, leaving 376 sq ft. At two coats that is 752 sq ft of paint, or 2.15 gallons at 350 sq ft per gallon. The 168 sq ft ceiling at one coat adds 0.48 gallons. The total is 2.63 gallons, so buy 3 gallons. One coat of primer on walls and ceiling needs about 3 gallons.
Frequently asked questions
How much area does a gallon of paint cover?
A gallon usually covers about 350 to 400 square feet. Check the can, since coverage varies by product and surface.
How many coats of paint do I need?
A common rule of thumb is two coats on walls and one on the ceiling. Porous or unpainted surfaces and big color changes can need more.
Do I subtract doors and windows?
For a more precise estimate, yes. Skipping the deductions builds in a small margin of extra paint, which many people like to have for touch-ups.
How much primer do I need?
A gallon of primer covers about 200 to 300 square feet, so you usually need slightly more primer than paint for the same single coat.
Estimates only. Textured or porous surfaces use more paint. Trim, doors and cabinets are not included.