How to Measure a Room for Area and Perimeter
To measure the area and the perimeter of a standard square or rectangular room, you can always use the simple formulas below.
How to Measure the Area (Square Footage) of a Room
Length x Width = Area
How to Measure the Perimeter (Distance Around) of a Room
Length + Width = Perimeter
Rectangular and Odd-Shaped Rooms
To measure a rectangular room, use a tape measure, pencil and paper to record the length and width of the room. Then multiply these numbers to get the total area of the room.
If the room you’re measuring has a closet, bay window or some other recess or protrusion, measure the shortest length and width of the room first. Multiply these measurements to get the main area of the room. Then calculate the area of the individual recesses by measuring their length and width. Lastly, add all of the areas together to get the total area of the room. You’ll use this process for T-shaped and L-shaped rooms as well.
When calculating the area of U-shaped rooms, use the same method of adding the individual areas together, omitting the area of any round recesses. Then calculate the area of a round recess: Measure through the center of the space to find the longest width and length of the recess. Next, divide the length in half and multiply that number by the width. Once you have this calculated, multiply the total by 3.14 (pi). This will give you the area of the complete oval. Because only half of the oval extends beyond your wall, divide the area in half. Now you have the area of the U-shaped protrusion in your room. You can add this number to the area of the other measurements in your room for the total area.
You can use our Square Footage Calculator to easily measure the main area of a room.
Walls
To calculate the area of a wall, use the standard formula of Length x Width = Area. Next, use the same formula to record the individual area of windows and doors. Once you have all of these measurements down, subtract the area of the windows and doors from the total area of the wall. This will help you calculate how much paint or wallpaper you need for a room without having lots of excess materials when you’re finished.
Watch our video for tips on how to use a tape measure correctly.
Don’t forget these best practices as you work:
- Ask a friend to help you take measurements. One of you can record while the other measures.
- Make sure there are no obstructions or obstacles that’ll throw your measurements off.
- Include a buffer of about 15% when purchasing materials. This will protect you from any unforeseen miscalculations and keep you from running short on supplies in the middle of your project.