Definition

Square foot (or sq. ft., ft²) is an imperial unit of area. The plural of square foot is square feet. The measurement unit is used mostly in the US, the UK, Singapore, Pakistan, Nepal, India, Malaysia, Ghana, Canada, Hong Kong and Bangladesh.

Square foot is used to indicate area in real estate, architecture, interior floor plan, as well as wall and roof.

Conversions 

1 square foot = 0.09290304 square meters

1 square foot = 144 square inches

1 square foot = 0.000022959 acres

1 acre = 43,560 square feet

1 square yard = 9 square feet

Calculation of square feet

The area of a room or space can be calculated by multiplying the length and width of the room/space. For example, if the room measures 10 feet by 10 feet, the area becomes 100 square feet and if the space measures 8 feet by 5 feet, the area comes to 40 square feet.

While measuring square feet, you need to remember that the figure given in square feet is the total area of a space and not the dimensions of the space. If a room has an area of 30 square feet, it does not mean that the space measures 30 feet by 30 feet. Rather, a room measuring 6 feet by 5 feet will have an area of 30 square feet. If the space measures 30 feet by 30 feet, its area would be 900 square feet.

Square feet in real estate

For real estate, square feet is calculated in two ways – one by measuring the dimensions of the house or property from outside and the other the internal carpet area of the property. Carpet area is the area which is enclosed within the walls of the property or actual area on which carpet can be laid.

In order to calculate square feet by measuring the external dimensions of a house, you need to measure the house from end-to-end or corner-to-corner. The exterior length and width of the house need to be added separately and then multiplied with each other. This calculation is called the built-up area.

Carpet area is the net usable area inside a house/property. This area excludes the space covered by external walls, terrace or balcony. It however includes the area of the inner walls of the property.

Built-up area = Carpet area + Area of inner walls + Area of terrace + Area of balcony

Finding square feet of non-square or non-rectangle space

Since a non-square or non-rectangle space will have more than one length and width, you need to divide the space into rectangles or squares. Thereafter, you will need to find the area of each of the individual spaces and add them.

Let us say the space is divided into 1 square and 2 rectangles. You can label them as 1, 2, 3 or A, B, C. If the square space measures 12 feet by 12 feet, then its area is 144 square feet. Similarly, we find out the area of the 2 rectangle spaces by multiplying their respective lengths with their respective widths. If the areas of the 2 rectangles come to 195 square feet (15 feet x 13 feet) and 72 square feet (12 feet x 6 feet),then the total area of the space becomes 411 square feet (144 square feet + 195 square feet + 72 square feet).