To find the square footage of something is the equivalent of asking the area of a two-dimensional shape or surface. Area is a measure of how much space something takes up in two dimensions. Generally, to determine area, you need two measurements: length and width. People use square footage for several reasons including estimating how much carpet or paint to buy or gauging how large their house is.

### Rectangle or Square

Measure one side of the rectangle. As an example, one side measures 4 feet.

Measure the adjacent side (not the opposite side) of the rectangle or square. In the example, the adjacent side measures 5 feet.

Multiply one measurement by the other to determine the square footage of the shape. In the example, 4 feet times 5 feet equals 20 feet squared, aka square feet.

### Triangle

Measure the base of the triangle. For example, say the base of a triangle measures 3 feet.

Measure the height of the triangle, which is the distance from the base to the top point. In our example, the height of the triangle is 5 feet.

Multiply the base by the height and divide by two to determine the square footage of the triangle. In our example, 5 feet times 3 feet equals 15 square feet, which divided by two equals 7.5 square feet.

### Circle

Measure the diameter of the circle from one side of the circle to the opposite side of the circle. For example, a circle has a diameter of 10 feet.

Divide the diameter by two to determine the radius. In our example, 10 feet divided by two equals a radius of 5 feet.

Square the radius. In our example, 5 feet squared equals 25 square feet.

Multiply the radius squared by pi. In our example, 25 square feet times 3.14 equals 78.5 square feet.