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Paint Calculator

Enter your room dimensions to find out exactly how much paint you need.

1. Room Dimensions
ft
ft
ft
2. Exclusions (Optional)
Standard door subtracts ~20 sq ft.
Standard window subtracts ~15 sq ft.
3. Paint Details
sq ft/gal

How to Calculate How Much Paint You Need?

Buying too much paint wastes money, and buying too little means an annoying extra trip to the hardware store in the middle of your project. Our Free Paint Calculator removes the guesswork by using standard contractor math.

The Paint Calculation Formula:

  1. Find the Total Wall Area: Add the length of all the walls you plan to paint together, then multiply that sum by the height of the room.
  2. Subtract Doors and Windows: A standard door takes up about 20 square feet (1.8 sq meters), and a standard window takes up about 15 square feet (1.4 sq meters). Subtract these from your total wall area to get your Paintable Area.
  3. Account for Coats: Multiply your Paintable Area by the number of coats you are applying (usually 2).
  4. Divide by Coverage: Divide that number by the paint's coverage rate. A standard gallon of premium interior paint covers about 350 to 400 square feet.

Frequently Asked Questions (FAQ)

How much paint do I need for a 12x12 room?

Assuming standard 8-foot ceilings, a 12x12 room has 384 square feet of wall space. If you subtract one door and one window, your paintable area drops to about 349 square feet. Since one gallon covers roughly 350-400 square feet, you will need two gallons of paint to comfortably apply two coats.

How many square feet does a gallon of paint cover?

On average, one gallon of interior acrylic/latex paint will cover between 350 and 400 square feet with one coat. However, rough or textured surfaces, unprimed drywall, and dark colors will absorb more paint, reducing the coverage rate.

Should I do one coat or two coats of paint?

Professional painters almost universally recommend two coats of paint. Even with premium "paint and primer in one" products, a second coat ensures true color accuracy, better durability, and eliminates patchy streaks.