Initial Paint Calculations

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

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 36 inches wide x 84 inches tall, a closet door 72 inches wide x 84 inches tall, and three windows 42 inches wide x 54 inches long. It will take two coats of paint to cover the walls. Each gallon of paint covers 350 square feet.

Add together all the lengths of the walls.

Wall A: 14 ft.

Wall B: 12 ft.

Wall C: 14 ft.

Wall D: + 12 ft.

52 ft. total

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

Total perimeter from Step 1: 52 ft.

Height of area to be covered: x 9 ft.

468 sq. ft.

Find the deductions of the doors in the room.

Door deductions: Add together the width of both the closet door and the door. Because these doors are 7 feet tall, you multiply the height by the door widths.

Find the deductions of the windows in the room.

Window deductions: Add together the width of all three windows. Because these windows are 4.5 feet tall, you multiply the height by the window widths.

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.

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.

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.

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.