Paint Calculator: How Much Paint Do I Need?

Pouring paint into tray

The Spruce / Margot Cavin

Get an estimate of how much paint you’ll need to buy for your next home project. It’s as simple as taking the following steps:

  1. Select the shape of your room.
  2. Find out the square footage of your walls by entering the width and height in feet. Enter the number of windows and doors in the room so we can subtract them from the total square footage. (You aren't painting over your windows, after all!)
  3. Press “calculate,” and get your results.

Editing Your Paint Calculation

You can edit your paint calculation at any point.

  • Editing square footage measurements: Update the width and/or height fields you would like to change, and press “calculate” again. To add extra walls and their measurements, press the plus sign next to “add wall.” To remove walls, press the trash can icon.
  • Starting over: To get a new estimate, select your desired room shape, and enter the new measurements. Then press “calculate” again. Note: Doing so will delete your current paint calculation, so be sure to make note of your results.

Understanding the Paint Calculator

The paint calculator is useful if you're planning an interior or exterior home painting project. Here are a few details so you can better understand how we came up with our calculations.

How Much Does a Gallon of Paint Cover?

  • One gallon of paint covers approximately 350 square feet.
  • A standard door accounts for approximately 20 square feet.
  • An average window accounts for approximately 15 square feet.

The Calculation

  • To find the area of a wall, we multiply wall height by wall width.
  • The estimate divides the total square footage by 350, as one gallon of paint covers 350 square feet.
  • Your paint calculation will update if you change the number of desired coats of paint.

Windows and Doors

On the right hand side of the calculator, you can select how many windows and/or doors are in the room you’re trying to paint so that the calculator knows not to count that square footage in the estimate. 

Ceiling Paint

If you’re planning on painting the ceiling of your particular room as well as the walls, you can click the checkbox next to “Ceiling Paint” on the calculator. Ceiling paint will be calculated as a separate item.

Coats of Paint

The calculator automatically accounts for two coats of paint. That's because adding a second coat of paint does two things: covers bare spots left behind from the first coat and creates a seal or barrier that makes the wall easier to clean.

When you calculate your results, you can change how many coats of paint you plan to add. Here's how to estimate how many coats of paint you might need:

  • High-quality paints with more pigments and resins may only require one coat.
  • If you are refreshing a wall with the same color of paint, one coat is all that's necessary.
  • If you are painting dark over light or light over a dark color that's primed over, two coats are best to cover and smooth over any bare or thin spots.
  • If you want your paint job to last longer, use two to three coats of paint, which will last significantly longer than a single coat.

Troubleshooting Errors With the Paint Calculator

Please make sure that you are using the most up-to-date version of your web browser in order to avoid potential errors.

Embedding the Paint Calculator

If you'd like to add this paint calculator to your site or blog, you can copy the provided embed code. Once you've finalized your measurements and other specifications, click or tap "Embed This Tool" to generate a code that you can insert into your website.