In this Instructable, you will learn how to determine the amount of paint needed to paint an interior room without excess overage or shortage.

## Step 1: Background Information

Your client wants her child’s bedroom painted. The room is 12 feet wide x 14 feet long with a ceiling height of 9 feet. In the room, there is one door 3 feet wide x 7 feet tall, a closet door 6 feet wide x 7 feet tall, and three windows 3.5 feet wide x 4.5 feet long. It will take two coats of paint to cover the walls. Each gallon of paint covers 350 square feet.

## Step 2: Find the Perimeter of the Room in Feet

Add together all the lengths of the walls.

## Step 3: Find the Square Footage That Needs to Be Covered

To get the square footage of the room, multiply the perimeter of the room by the wall height.

## Step 4: Determine Door Deductions in Feet

Find the deductions of the doors in the room.

Door deductions: Multiply the height and width of each door in the room (the door and the closet door) and add together.

## Step 5: Determine Window Deductions in Feet

Find the deductions of the windows in the room.

Window deductions: Multiply the height and width of a window. Because all of the windows are the same size, and there are 3 of them in the room, multiply by 3.

## Step 6: Determine Total Deductions in Feet

Find the total deductions in the room.

Deductions: Add together the total from the door and the window deductions to find the total deductions in the room.

## Step 7: Determine Square Footage of Paint Needed

You now have your total square footage and your deduction total.

Subtract the deduction total from the total square footage, and multiply by the number of paint coats that will be used to get the total square footage of paint that is needed.

## Step 8: Determine Gallons of Paint Needed

You just found the total amount of paint that will be needed.

Since each gallon of paint covers 350 square feet, divide the total amount of paint by 350.

If the resulting number is a decimal, round up to the nearest whole number.

For this specific room, 3 gallons of paint should be purchased.

## Step 9: Conclusion

You now know how to calculate the amount of paint that is needed for a space. This Instructable can be used for any interior room in a building.