Room Paint Estimator

Paint coverage depends on wall area, surface texture, paint quality, and number of coats. One gallon of paint typically covers 350–400 square feet (32–37 m²) on smooth surfaces.

The formula: Wall area = (Room perimeter × Wall height) - (Door area × Doors) - (Window area × Windows) Gallons needed = (Wall area × Coats) / Coverage per gallon

Standard dimensions used:

• Door: 21 sq ft (3 ft × 7 ft / 0.9 m × 2.1 m)
• Window: 15 sq ft (3 ft × 5 ft / 0.9 m × 1.5 m)
• Standard coverage: 350 sq ft per gallon (smooth wall, quality paint)

Coverage varies by surface:

• Smooth drywall: 350–400 sq ft/gallon
• Textured drywall: 300–350 sq ft/gallon
• New/unpainted drywall: 250–300 sq ft/gallon (absorbs more)
• Previously painted (same color family): 350–400 sq ft/gallon
• Dark to light color change: 250–300 sq ft/gallon (may need 3 coats)

Number of coats:

• Same color touch-up: 1 coat
• Similar color change: 2 coats (standard)
• Drastic color change (dark to light): 2–3 coats
• New construction (bare drywall): 1 primer + 2 coats

Paint quality matters:

• Budget paint ($20–30/gallon): Lower pigment density, may need extra coats
• Mid-range ($30–45/gallon): Good coverage, 2 coats usually sufficient
• Premium ($45–70/gallon): Best coverage, sometimes 1 thick coat is enough

Tip: Always buy 10% more paint than calculated. Touch-ups, mistakes, and slightly different coverage rates mean you will almost certainly need a little extra. Unused paint can be sealed and stored for years for future touch-ups.

Ceiling paint: If painting the ceiling, add room length × width to your total area. Ceiling paint is typically flatter (less reflective) and thicker than wall paint.