Paint Calculator
Enter your wall area and number of coats to see how much paint to buy — no half-used cans, no second trip to the store.
How to use the Paint Calculator
- Measure wall area: room perimeter × wall height, or enter a known total.
- Subtract doors and windows (~21 ft² and ~12 ft² each).
- Set coats — two coats is standard for a color change.
- Adjust coverage if your paint label states it (typical: 350–400 ft² per gallon).
Formula & methodology
Paint = (Area − openings) × Coats ÷ Coverage per gallon. Typical interior acrylic covers about 400 ft² per gallon per coat on primed walls.
Example
Walls totaling 400 ft² with 40 ft² of openings, two coats at 400 ft²/gal: (400 − 40) × 2 ÷ 400 = 1.8 gallons — buy two.
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FAQ
How much does one gallon of paint cover?
Most interior paints cover 350–400 ft² per gallon per coat. Rough or unprimed surfaces drink more — check your label.
Do I need two coats?
Two coats give even color and durability. One coat can work for touch-ups or painting over a similar color with a quality primer underneath.
Does paint color affect coverage?
Yes — deep reds, oranges and yellows often need an extra coat or a tinted primer. Buy quality paint; cheap paint needs more coats.
Should I paint walls or trim first?
Pros typically cut in and roll ceilings, then walls, then paint trim last — butts and casing are easiest to touch up at the end.