How Much Paint Do I Need For My Project?

Painting your home can transform it from drab to fab in just a few strokes. But somewhere along the way, you’ll probably ask yourself, “How much paint do I need?” With a little bit of simple math, you can figure out exactly what you need and avoid having to throw away leftover paint.

How Much Paint Do I Need for Different Rooms

A gallon of paint covers around 400 square feet, while primer covers 200 to 300 square feet. If you’re painting a single room, you may only need one gallon of paint. However, if you need to use primer, do multiple coats, or paint an entire floor of your home, your paint needs will increase.

Calculating How Much Paint You Need

To figure out how much paint you need for your project, you’ll need to calculate the square footage of the walls that need to be painted (more on that below). Once you have that figure, the following formula can help you determine how much paint you need:

Wall square footage - door and window square footage x 10% to 15% wastage = total paintable wall space

Once you have the total paintable square foot, apply the following formula:

Square footage / 400 = gallons of paint needed

How to Measure a Room for Painting

Before you head to the paint store, you should calculate how much paint you need. A gallon of paint costs between $20 and $70, so buying more than you need can waste quite a bit of money. Knowing that a gallon of paint covers around 400 square feet, you can determine how much you’ll need by calculating the total square footage of the walls to be painted.

Calculating Paint Needed for a Room

To determine how much paint you need in a basic room, you’ll need to calculate the room’s square footage by taking the following steps.

1. Measure the lengths of each wall from corner to corner.

2. Measure the height of each wall from floor to ceiling.

3. Multiply the length of each wall by the height to get the square footage.

4. Add the square footage of each wall together to get the total square footage of the room.

5. Subtract the size of any windows and doors in the room.

6. Multiply the total square footage by 0.10 or 0.15 to account for wastage.

7. Divide the total number by 400 to calculate the gallons of paint you need.

For example, a room with 400 square feet of paintable walls would require one gallon of paint for one coat or two gallons of paint for two coats. You may be able to stick with one coat if you’re painting over a similar color, but it’s often best to plan for two coats to avoid any streaks.

Calculating Door and Window Size

If there are doors and windows in the room you want to paint, you’ll need to calculate their size and subtract that number from the room’s square footage. Here’s how to do that.

• Measure the door or window area, including the frame and glass

• Add the area of all doors and windows together

• Subtract that number from the wall square footage

For example, a room that has 400 square feet of wall space and 50 square feet of window and doors will have a total paintable area of 350 square feet, requiring just under one gallon of paint (or two if you want to do a second coat).

Calculating Paint Needed for Ceilings

If you want to paint the ceiling, you’ll need to measure it as well. To do so, take the following steps:

1. Measure the ceiling’s length and width

2. Multiply the numbers to calculate the total square footage

3. If you want to paint the ceiling the same color as the walls, add the ceiling square footage to the wall square footage

For example, a 10-foot-by-12-foot ceiling measures 120 square feet. Adding that to our 350-square-foot wall brings the total paintable area to 470 square feet, or just over one gallon of paint for one coat or around 2.35 gallons for two coats.

Who to Hire to Paint Your Home

Painting your home as a DIY project can save you money on labor. However, it’s a time-consuming and physically demanding project. If you prefer to leave painting to the pros, you can hire a local interior painter to paint your home for you. A pro will know how many coats are needed based on your home size and can often get discounts on supplies from local paint stores. Expect to pay around $400 to $1,600 for the cost to paint a room using a pro.