Paint Cans Calculator
"A gallon covers 400 sq ft" is the slogan. This is the math that accounts for your windows, your second coat, and the roller's honest coverage.
Buy in whole gallons. The "quart top-up" row is for trim/patch work, a quart covers ~100 sq ft.
How the math works
- Wall area = 2 × (width + length) × height. Windows subtract count × avg area; doors subtract 21 sq ft each.
- Ceiling (optional) adds width × length at its own coat count.
- Gallons = area × coats ÷ coverage, rounded up to the next whole gallon; 5% waste for roller dead-zones is inside the coverage defaults.
- Coverage tiers: 400 = slick new drywall, 350 = normal repaint, 300 = textured, porous, or dark-to-light without primer. Primer counts as a coat.
How many gallons to paint a 12×14 room with 8-foot ceilings?
Perimeter walls (78 sq ft after two windows and a door) in 2 coats ≈ 2 gallons; add a gallon for the ceiling. Standard bedroom: 2–3 gallons.
Does the second coat use the same amount of paint?
Less. The first coat soaks into bare/porous wall; the second rides on top. The tool charges full coverage for coat 1 and lets the tier you picked average it out, buying the full 2-coat amount is the safe answer.
Do I prime?
Dark→light, patched drywall, stains, and new bare board all need primer, count it as a coat (3-coat setting). Repainting a similar color over sound paint: 1 coat is often enough.