Paint Calculator
Enter your wall area and how many coats you're applying, and this gives the gallons of paint to buy — using the coverage figure for your paint.
Paint needed
2.1gal
- Round up to buy
- 3 gal
- Area painted
- 400 sq ft
How it’s calculated
Paint = (wall area − large openings) × coats ÷ coverage per gallon. Coverage is printed on the can and varies with the surface — about 350–400 sq ft per gallon on smooth, sealed walls, and less on rough, porous, or bare drywall. Paint is sold by the gallon (and quart), so round the result up.
Worked example
400 sq ft of wall, 2 coats, paint covering 375 sq ft/gal, no openings subtracted: 400 × 2 ÷ 375 = 2.1 gallons → buy 3 gallons (or 2 gallons plus a quart).
FAQs
- How much area does a gallon of paint cover?
- About 350–400 sq ft per coat on a smooth, primed wall — the figure on the can. Rough, textured, porous, or bare-drywall surfaces drink more and cover less, so use the low end (or your can's number) for those. That's why coverage is an input here, not a fixed number.
- How many coats do I need?
- Two is the norm for even color and full coverage. One coat can work when repainting a similar color over a sound surface; three when a light color has to cover a dark one. Bare drywall and big color changes usually want a primer coat first, which is separate from the finish coats.
- Should I subtract doors and windows?
- Subtract only the large openings — a few big windows or a sliding door — and enter their area in square feet, not a count (a 3×7 ft door ≈ 21 sq ft). Skip small ones and outlets; the rounding and a little waste for touch-ups absorb them. Don't subtract so much that you come up short — running out mid-wall risks a visible lap mark.
Sources
- Paint = (area − openings) × coats ÷ coverage per gallon, rounded up to whole gallons. Coverage (~350–400 sq ft/gal on smooth primed walls) is product/surface-specific (from the can) — editable, not baked in.