Paint Coverage Calculator
Enter the total wall area you are painting and how many coats you plan, and find out how much paint to buy — no mid-project store runs.
Runs entirely in your browser — your numbers never leave this page.
How it works
Paint math is simple division — the trick is measuring honestly and rounding up:
Gallons needed = Wall area (sq ft) × Coats ÷ Coverage per gallon
- Example: 400 sq ft of wall, 2 coats, 350 sq ft/gal paint → 800 ÷ 350 ≈ 2.29 gallons → buy 3 gallons.
- Always round up to whole gallons. Running out mid-wall leaves a visible lap line where the new batch meets the old. Leftover paint is touch-up gold.
- Quarts cost more per ounce — the quart figure is there for tiny jobs. For anything over a gallon, buy gallons.
- Porous surfaces (bare drywall, brick, heavy texture) absorb more — add 10–25% or prime first.
Frequently asked questions
How do I measure a room for paint?
Measure each wall: length × height, then add all walls together. For precision, subtract about 21 sq ft per door and 15 sq ft per average window. A 12×12 ft room with 8 ft ceilings is roughly 384 sq ft of wall before deductions.
Is one coat of paint ever enough?
Sometimes — if you are repainting the same color with quality paint over a sound surface. For color changes, new drywall, or cheap paint, two coats is the rule: the first coat seals, the second gives true color and durability.
Do I need primer, or is paint-and-primer enough?
Paint-and-primer combos are fine over previously painted walls. Use a dedicated primer for bare drywall, bare wood, drastic color changes (dark to light), stains, or glossy surfaces that need grip.
Does ceiling paint cover differently?
Coverage per gallon is similar (~350 sq ft), but use flat ceiling paint — it hides flaws and does not reflect light unevenly. Ceilings usually take one coat unless stained.
How much paint do I need for trim and doors?
Rough guides: one average interior door (both sides) takes about 1 quart; baseboards and trim for one room take about 1 quart; a whole house of trim can take a gallon or more. Trim paint is usually semi-gloss.
Why does textured paint coverage vary so much?
Knockdown, orange-peel, and especially popcorn textures have far more surface area than flat drywall — they can drink 10–25% more paint. Budget for it or back-roll to work paint into the texture.
Does spraying use more paint than rolling?
Yes — typically 10–20% more due to overspray and the thinner coat sprayers lay down. Sprayers are faster on big empty spaces; rollers waste less on occupied rooms.
What paint sheen goes where?
Flat: ceilings and low-traffic walls (hides flaws). Eggshell/satin: living rooms and bedrooms (washable). Semi-gloss: trim, doors, kitchens, baths (moisture-resistant, scrubbable).
How do I store leftover paint?
Seal the can tightly (tap the lid with a mallet, not a hammer), store upright in a cool, dry place — never where it freezes. Write the room and date on the lid. Properly stored latex lasts 5–10 years.
How long between coats?
Follow the can — typically 2–4 hours for latex to recoat. Painting too soon traps moisture and ruins adhesion. In humid weather, wait longer.