Paint Calculator: How Many Gallons of Paint You Need

Determine how many gallons of paint you need by entering the width and height of the area you’re painting in feet. We’ll also show you how to calculate your paint needs with an easy to use formula.

How Much Paint Do I Need: Calculator

One gallon of paint covers about 350 square feet of wall with one coat. To determine how many gallons of paint, calculate the square footage of the walls in your room and desired number of coats. Determine wall square footage by multiplying the width by the height of each wall in feet and then add them all together.

Gallons of paint = (wall square footage ÷ 350) x desired number of coats

How to Determine How Much Paint You Need

To determine your paint needs, you’ll need to figure out the square footage of your wall area by multiplying the width x height of each wall.

Example: A square 12’ x 12’ room with 8-foot ceiling height

• Step 1: Multiply the width x height of each wall. Since each wall is 12 feet wide by 8 feet high, we’ll multiply 12 x 8 = 96 square feet
• Step 2: Add the square footage of all walls together. Since all of our walls are the same, we can multiply 96 x 4 for a total of 384 square feet.
• Step 3: Divide the wall square footage by 350 to determine how many gallons of paint you’ll need for one coat. 384 ÷ 350 = 1.10
• Step 4: Multiply your answer by the desired number of paint coats. For example, if you’d like two coats of paint on the wall, multiply 1.10 by 2 for a total of 2.20 gallons. You can round this up to three gallons of paint.

Example: Calculating paint for an irregularly shaped room

• Step 1: Multiply the width x height in feet of each wall to determine square footage.
• Step 2: Add the square footage of all walls together for the total.
• Step 3: Divide the total square footage by 350 to determine how many gallons of paint it would require to give all walls one coat.
• Step 4: Multiply this number by the desired coats of paint.

Deducting Doors and Windows from Paint Estimates

You probably have at least two doors and one window in your room. If you want to ensure you have plenty of extra paint, there’s no need to deduct wall and door square footage. However, if you want more exact estimates, you can subtract door and window square footage from your gallons of paint estimate.

• Standard interior door size is 80 inches by 32 inches, which equals about 18 square feet. You can deduct 18 square feet for every door in the room.
• Average standard residential window size is about 24 inches by 36 inches or 6 square feet. Deduct six square feet for every window in your room.

If your windows or doors are not standard sizes, determine the square footage by multiplying the length by the width in feet.

Are Paint Estimates Accurate?

Paint estimates give you a general idea of how many gallons of paint you’ll need but are not exact. For example, if you have new drywall, you’ll need a primer and possibly more paint than estimated since fresh drywall is porous. On the other hand, paint estimates are more accurate for walls with existing paint since they’re less likely to soak up the product. Other factors that influence accuracy include the quality of the paint, the previous color on the wall, and whether you added a primer.