Paint Calculator – Room Coverage Estimator
Estimate how much paint you need based on room dimensions and number of coats.
How to Calculate Paint Coverage
Standard interior paint covers approximately 350–400 sq ft per gallon (one coat). To find the area to paint: measure the perimeter of the room × ceiling height for walls, then subtract doors (~20 sq ft each) and windows (~15 sq ft each).
Example: a 12 × 14 ft room with 9 ft ceilings, 1 door, 2 windows: Perimeter = (12+14) × 2 = 52 ft. Wall area = 52 × 9 = 468 sq ft. Subtract 20 + 30 = 50 sq ft → 418 sq ft. At 400 sq ft/gallon, you need slightly over 1 gallon for one coat. For two coats: 2+ gallons.
Primer, Paint Types, and Finishes
Primer: Use when painting over fresh drywall, dark colors, or stains. Dramatically improves coverage and adhesion — one coat of primer + one coat of paint often beats two coats of paint alone.
Finishes: Flat/matte (hides imperfections, not washable — bedrooms); Eggshell (slight sheen, washable — living rooms); Satin (more sheen, very washable — hallways, kids rooms); Semi-gloss (high sheen, moisture resistant — bathrooms, kitchens, trim); Gloss (maximum durability — doors, furniture).
Pro Painting Tips
Always buy slightly more than calculated — nothing is worse than running out mid-wall. Paint can be stored for 2+ years sealed. Use the same batch (same lot number) for consistent color. Work top to bottom: ceiling first, then walls, then trim. Cut in (brush along edges) before rolling. Allow proper drying time between coats (typically 2–4 hours for latex, 24 hours for oil-based).
Frequently Asked Questions
How many coats of paint do I need?
Two coats is standard for most paint jobs. One coat may suffice when repainting the same color. Three coats may be needed when painting white over a dark color or when dramatic color change. Primer counts as one of your coats if using paint+primer in one.
Latex vs oil-based paint: which should I use?
Latex (water-based): easy cleanup, fast drying, low VOC, flexible — best for walls, ceilings, and most interior surfaces. Oil-based: harder, more durable, slower drying, strong odor — best for high-traffic surfaces, metal, and exterior wood.
How do I calculate ceiling paint?
Simply measure the room dimensions: Length × Width = ceiling area in sq ft. A 12 × 14 ft room has a 168 sq ft ceiling. Divide by coverage (350–400 sq ft/gallon) = ~0.4–0.5 gallons. One gallon is usually plenty for an average room ceiling with one coat.