Find out how many gallons of paint and primer your project needs. Enter the total wall area, number of coats, and your paint’s coverage rate — the calculator rounds up to whole gallons and adds your waste factor.
Loading calculator…
How to use this calculator
- Enter the total wall area in square feet. Don’t know it? Measure each wall’s length × height and add them up — or use our square footage calculator.
- Choose coats — 2 is standard for color changes.
- Check your paint can for coverage per gallon (usually 300–400 sq ft).
- Add the price per gallon for a cost estimate.
The math behind it
Gallons = wall area × coats ÷ coverage per gallon, plus waste, rounded up to whole gallons. Primer = wall area ÷ 300 sq ft per gallon, rounded up.
FAQs
How much paint do I need for a 12×12 room?
A 12×12 room with 8 ft ceilings has about 384 sq ft of wall (minus doors/windows). Two coats at 350 sq ft per gallon = roughly 3 gallons, plus 1–2 gallons of primer for a color change.
Do I need primer?
For drastic color changes, new drywall, or stained walls — yes. For a same-color refresh on previously painted walls in good condition, two finish coats are usually enough.