A fresh coat of paint can change the face of a room, but painting is a home improvement task that requires planning. Repair projects will run more smoothly if you know how much paint you need before you start painting the room. Follow these steps to calculate the amount of paint needed.
Step
Step 1. Measure the dimensions of the room
Start by noting the width and height of each side of the wall.
Step 2. Determine the surface area of the wall in square feet or square meters
For example, if the side wall is 15 feet (4.6 m) wide and 10 feet (3.1 m) high, the surface area of the wall is 150 square feet (14.26 square meters). If the walls of the longer room are 20 feet (6.1 m) wide, the surface area of each side of the wall is 200 square feet (18.91 meters). The opposite walls of a standard room will have the same surface area.
Step 3. Find the total surface area of the initial wall by adding up the area of the four sides of the wall
In the example, the initial wall surface area is 700 square feet (150+150+200+200=700) or 66.34 square meters (14, 26+14, 26+18, 91+18, 91=66, 34). Record the results on a piece of paper.
Step 4. Calculate the area of the doors and windows
Subtract the surface area of the door, including the frame, and the window when calculating the amount of paint needed. For example, in a room with a surface area of 700 square feet, there are 2 doors and 1 window. 1 door, including the frame, is 4 feet (1.2 m) wide and 8 feet (2.4 m) high. The other door measures 10 feet (3 m) by 8 feet (2.4 m). The windows are 10 feet (3 m) wide and 4 feet (1.2 m) high. The total surface area of this area is 152 square feet (32+80+40=152) or 13, 68 (2, 88+7, 2+3, 6=13, 68).
Step 5. Calculate the net surface area
Subtract the area of the doors and windows from the total surface area of the four walls. In the example, the result is 548 square feet (700-152=548) or 52.66 square meters (66, 34-13, 68=49, 32).
Step 6. Take into account special conditions
You may want to paint certain areas, such as window sills, the same color as the walls. You can add some area to the calculation by adding 10 percent to the net surface area. In this case, you need to add enough paint to account for the additional 54.8 square feet or 5 square meters of area.
Step 7. Calculate the door, door frame, and baseboard
Most people paint this area the same color, but choose a different color than the one used for the walls.
- In the example, the surface area of the door is 112 square feet (10.4 square meters). The baseboard, if available, is usually about 3 inches (7.6 cm) high and will extend around the perimeter of the room, minus the space for the door frame. The two doors in the example are on the same 20 feet (6 meters) long wall. One door is 4 feet (1.2 m) wide and the other is 8 feet (2.4 m) wide. This means that the baseboard on the wall is 8 feet (2.4 m) long. The other baseboards are 15 feet (4.6 m), 15 feet (4.6 m), and 20 feet (6.1 m) long. The total linear area of the baseboard is 58 feet (17,678 m).
- Convert the surface area of the 3-inch (7.6 cm) baseboard to square feet. Divide the total linear area by 4.58 feet/4=14, 5 square feet. To paint the door, door frame, baseboard in the example, you will need enough paint to cover an area of 126 square feet. Add 20 percent to this number to account for the door frames and finishes, for a total of 151 square feet.
Step 8. Calculate the surface area of the ceiling
Measure the width and length of the floor. Multiply both. This is the surface area, minus the ventilation area and various fixed fixtures. In the example, the ceiling is 200 square feet. Textured ceilings may need a little extra paint.
Step 9. Calculate the amount of paint needed to paint the room
Estimate between 350 and 400 square feet per gallon of paint on smooth interior plaster walls. In this example, you will need about 2 gallons (4 liters) of paint to cover the walls with one coat. If you want to paint your doors, door frames, plinths, and ceilings the same color, you'll need additional paint. Use this parameter if you paint using a brush or roller. If using a spray, you will need about 10 percent additional paint.
