Paint Calculator
Calculate how many gallons of paint you need for a room, including ceiling, multiple coats, and optional primer.
Typical coverage: 350–400 sqft/gal on smooth painted surfaces; 250–300 on new drywall or rough texture.
Paint Needed
2.8 gallons
480 sqft paintable · 2 coats · ~$135 est. cost
| Wall Area | 396 sqft |
| Deductions (1D + 1W) | −36 sqft |
| Ceiling Area | 120 sqft |
| Paintable Area | 480 sqft |
| Paint (2 coats @ 350 sqft/gal) | 2.8 gal |
| Est. Paint Cost | ~$135 |
| Total Est. Cost | ~$135 |
Paintable area = perimeter × height + ceiling (if selected), minus door and window deductions. Gallons = area × coats ÷ coverage. Coverage defaults to 350 sqft/gal — reduce to 300 for new drywall or rough surfaces. Primer calculated at 300 sqft/gal. Cost estimates use $45/gal for paint and $30/gal for primer — use actual product pricing for final quotes.
Frequently Asked Questions
How many gallons of paint do I need for a 12×10 room?
For a 12×10 room with 9-ft ceilings, 1 door, and 1 window: walls = 2 × (12+10) × 9 = 396 sqft, minus 21 (door) and 15 (window) = 360 sqft wall area, plus 120 sqft ceiling = 480 sqft total. At 350 sqft/gal with 2 coats = 480 × 2 ÷ 350 ≈ 2.75 gallons. Round up to 3 gallons to be safe.
What does paint coverage mean?
Coverage is the square footage one gallon of paint covers in a single coat — typically 350–400 sqft/gal for latex on smooth, previously painted surfaces. Porous or rough surfaces (new drywall, bare wood, rough texture) absorb more and yield 250–300 sqft/gal. Always use the lower end for bidding to avoid running short.
Do I need primer before painting?
Yes, in these situations: new drywall (drywall paper is very porous), major color changes from dark to light, surfaces with stains or water damage, or bare wood. One coat of quality primer effectively replaces one coat of paint and improves adhesion, color uniformity, and final coverage. Skipping primer on new drywall leads to “flashing” — uneven sheen that shows through the paint.
How much does interior paint cost?
Quality interior latex ranges from $35–65 per gallon at retail. Budget $45/gal as a rule of thumb for estimating — use the actual product spec for final quotes. Premium paints in the $55–65 range often deliver better coverage and hide, sometimes reducing the total gallons needed. Contractor accounts at paint stores typically save 20–30% off retail.