Paint Coverage Calculator
Calculate how many gallons of paint you need by room dimensions, paint type, coats, and cutouts for doors and windows.
Based on Satin paint at 350 sq ft/gal coverage. Cost estimate assumes $25–$50 per gallon.
How It Works
This calculator estimates gallons of paint based on your room dimensions, paint type, number of coats, and openings. It deducts ~21 sq ft per door and ~15 sq ft per window from the total wall area.
Formula: Wall Area = 2 × (Length + Width) × Height − (Doors × 21) − (Windows × 15). Gallons = (Total Area × Coats) ÷ Coverage per Gallon.
Coverage varies by paint type: Primer ~200 sq ft/gal, Flat ~400 sq ft/gal, Eggshell ~375 sq ft/gal, Satin & Semi-Gloss ~350 sq ft/gal. Results are rounded up to full gallons.
Frequently Asked Questions
How do I calculate paint coverage for a room?
Measure each wall's length and multiply the room perimeter by the wall height to get total wall area. Subtract about 21 sq ft per door and 15 sq ft per window. If painting the ceiling, add length × width. Multiply total area by the number of coats, then divide by the paint's coverage rate (typically 350–400 sq ft per gallon).
What is the coverage rate for different paint types?
Flat paint covers about 400 sq ft per gallon. Eggshell covers roughly 375 sq ft, while satin and semi-gloss cover around 350 sq ft per gallon. Primer has lower coverage at about 200 sq ft per gallon because it must seal the surface thoroughly.
Should I include the ceiling in my paint estimate?
Include the ceiling if you plan to paint it. Ceiling paint is usually flat white, and coverage is about the same as flat wall paint (400 sq ft/gal). Ceilings often need only one coat if using ceiling-specific paint.
How many coats of paint do I need?
Most paint jobs require two coats for even coverage and durability. One coat may work when repainting the same color with a high-quality paint-and-primer-in-one. Three coats are sometimes needed when covering very dark colors or painting over bare drywall.
How much does a gallon of paint cost?
Interior latex paint ranges from $25–$50 per gallon depending on quality and brand. Budget paints start around $25, mid-range paints run $30–$40, and premium paints (Benjamin Moore, Sherwin-Williams) cost $40–$50+ per gallon.