🎨 Paint Calculator

Calculate how much paint you need for your room. Account for doors, windows, coats, and estimate total cost.

sq ft
sq ft
sq ft/gal
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💡 Standard interior paint covers about 350-400 sq ft per gallon. Premium paint can cover 300-350 sq ft.

Total Wall Area 432 sq ft
Openings Area 51 sq ft
Paintable Area 381 sq ft
Paint Needed 2.18 gallons
Gallons to Buy 3 gallons
Paint Needed (Liters) 8.24 liters
Estimated Cost $105.00 USD

How to Calculate How Much Paint You Need

Estimating paint quantity accurately saves money and prevents waste. Our paint calculator helps you determine exactly how many gallons of paint you need for your room, accounting for doors, windows, and the number of coats.

Paint Calculation Formula

Paintable Area = (2 × (Length + Width) × Height) − Doors − Windows

Gallons Needed = (Paintable Area × Number of Coats) ÷ Coverage per Gallon

Average Paint Coverage

Paint Type Coverage (sq ft/gal) Best For
Flat / Matte 350-400 Ceilings, low-traffic areas
Eggshell 350-400 Living rooms, bedrooms
Satin 350-400 Kitchens, bathrooms, hallways
Semi-Gloss 350-400 Trim, doors, cabinets
High-Gloss 300-350 Furniture, accents
Primer 200-300 New drywall, color changes

Paint Needed for Common Room Sizes

Use this quick reference table to estimate paint for standard room sizes (8-foot ceilings, 2 coats, 350 sq ft/gallon coverage):

Room Size Wall Area Paintable Area* Gallons (2 Coats)
8×10 ft 288 sq ft 252 sq ft ~2 gallons
10×10 ft 320 sq ft 284 sq ft ~2 gallons
10×12 ft 352 sq ft 316 sq ft ~2 gallons
12×12 ft 384 sq ft 348 sq ft ~2 gallons
12×14 ft 416 sq ft 380 sq ft ~3 gallons
12×15 ft 432 sq ft 396 sq ft ~3 gallons
14×16 ft 480 sq ft 444 sq ft ~3 gallons
16×20 ft 576 sq ft 540 sq ft ~4 gallons

*Paintable area assumes 1 door (21 sq ft) and 1 window (15 sq ft) subtracted.

Pro Tips to Save Money on Paint

  • Buy quality paint. Premium paint covers better and lasts longer, meaning fewer coats and less repainting in the future.
  • Use primer on new walls. A good primer costs less than paint and improves coverage, potentially saving you a whole coat of paint.
  • Buy in 5-gallon buckets if painting multiple rooms the same color — it's 10-20% cheaper per gallon.
  • Keep leftover paint sealed for touch-ups. Stored properly, latex paint lasts 2-10 years.
  • Don't forget the ceiling. If painting ceilings too, add room length × width to your total area.

Frequently Asked Questions

How many gallons of paint do I need for a 12×12 room?

For a 12×12 room with 8-foot ceilings, the total wall area is about 384 sq ft. Subtract one door (21 sq ft) and two windows (30 sq ft), leaving 333 sq ft of paintable area. At 350 sq ft per gallon, you need about 1 gallon per coat. With 2 coats, plan for 2-3 gallons total.

How much does a gallon of paint cover?

A gallon of interior paint typically covers 350-400 square feet with one coat on smooth surfaces. On textured or porous surfaces, coverage drops to 250-350 sq ft. Premium paints may cover slightly less at 300-350 sq ft per gallon.

Do I need 2 coats of paint?

Yes, most painting projects require 2 coats for even coverage, color depth, and durability. You may need only 1 coat if painting over a similar color with a high-quality paint-and-primer-in-one. Always use 2 coats when changing from dark to light or painting new drywall.

How much paint do I need for a ceiling?

Multiply room length by width to get the ceiling area. For a 12×15 room, that's 180 sq ft. At 350 sq ft per gallon, you need about 0.5 gallons per coat, or 1 gallon for 2 coats.

Should I subtract doors and windows?

Yes! A standard interior door is about 21 sq ft (3ft × 7ft) and a standard window is about 15 sq ft (3ft × 5ft). Subtracting these ensures you don't overbuy paint.

How much paint do I need for a 10×10 room?

A 10×10 room with 8-foot ceilings has 320 sq ft of wall area. After subtracting a door and window (about 36 sq ft), you have 284 sq ft to paint. That's about 0.8 gallons per coat, or roughly 2 gallons for 2 coats.

How do I calculate paint for multiple rooms?

Calculate each room separately, then add up the total gallons needed. Buying in bulk (5-gallon buckets) is more cost-effective if painting multiple rooms the same color.

What is the difference between interior and exterior paint coverage?

Interior paint covers about 350-400 sq ft per gallon on smooth walls. Exterior paint covers 250-350 sq ft per gallon due to rougher surfaces like stucco, wood siding, or brick. Always use exterior-rated paint for outside projects.