A room measuring 10 feet by 8 feet has an area of 80 square feet. Rectangular area is determined using the base times height formula (A=b*h).
Unlike perimeter, which measures the exterior of a 2-dimensional structure, area measures the interior. Using a field as an example, the grassy inside of the field would be measured using the area method, while the fencing would be measured using the perimeter formula.
The answer to a problem involving area is expressed in units squared. When selecting paint, it is useful to know the area of each wall in a room. When selecting floor coverings, it is advantageous to know the size of the floor or base.