Estimate how much paint you need before you buy. Enter room length, width, and height (or total wall area), choose coats, coverage rate, and an optional waste factor, then subtract doors and windows. Results show net wall area, area after coats, gallons (rounded up), and liters — a practical materials estimate for DIY painting projects.
Estimate how much paint you need before you buy. Enter room length, width, and height (or total wall area), choose coats, coverage rate, and an optional waste factor, then subtract doors and windows. Results show net wall area, area after coats, gallons (rounded up), and liters — a practical materials estimate for DIY painting projects.
A 12 × 10 ft room with 8 ft ceilings has 352 sq ft of wall surface. Subtract 40 sq ft of doors and windows → 312 sq ft net. Two coats → 624 sq ft. Add 10% waste → 686.4 sq ft. At 350 sq ft/gal that is 1.961 gallons, rounded up to 1.97 gal (≈ 7.46 L).
gross = 2×(L+W)×H × (walls/4); net = max(0, gross − openings); withCoats = net × coats; withWaste = withCoats × (1 + waste%/100); gallons = ceil_0.01(withWaste / coverage); liters = gallons × 3.78541
Estimates are for planning materials only. Check the paint label for actual coverage and buy enough for touch-ups.
Measure length, width, and ceiling height in feet. Wall area for a four-wall rectangular room is 2 × (length + width) × height. Subtract doors and windows, multiply by the number of coats, add a waste factor if desired, then divide by the paint’s coverage (often about 350 sq ft per gallon). This calculator does those steps and rounds gallons up to the nearest 0.01.
Use the manufacturer’s stated coverage on the can when available. A common default for smooth interior walls is about 350 square feet per gallon per coat. Rough texture, primer-only products, or deep colors may cover less — lower the coverage number to buy more paint.
Waste covers roller absorption, cut-in overlap, touch-ups, and porous surfaces. 10% is a practical DIY default. Use 5% for smooth primed walls with careful application, or 15%+ for textured walls, dark-to-light color changes, or first-time painters.
Yes, if they take meaningful wall space. A standard interior door is roughly 20 sq ft; a typical window might be 12–15 sq ft. Enter the combined opening area in the doors & windows field so net wall area is not overstated.
No. This tool estimates vertical wall paint only. For ceilings, use total area mode with length × width (or measure separately). Trim and doors are usually a different sheen and should be estimated on their own.
Results use 1 US gallon = 3.78541 liters. Gallons are computed first (rounded up to 0.01), then multiplied by that factor so metric shoppers can compare can sizes.