Students commonly make the mistake of finding area instead of perimeter, or vice versa. In simplest terms: area is the amount of space inside a shape, and perimeter is the distance around the outside of the shape.
What is Area?
Area measures the number of square units that can fit on the inside of a shape. If you copied a shape onto grid paper, the area would be the number of squares that the shape covers up. There are many different formulas for area that depend on the shape, but the main idea is that area is the amount of space on the inside of the shape. 10 squares fit inside the shape below, so the area is 10 square units.
Units for Area
Area is the number of squares that fit in the inside of the shape so it is always measured in square units (square meters, square inches, square feet, etc.).
What is Perimeter?
Perimeter measures the distance around the outside of the shape. Think about it as if you're about to put a fence around the outside of the shape and you need to know the length of the fence. If you count the spaces around the outside of the shape below, you'll find that the distance around it is 14. This means the perimeter is 14 units.
Units for Perimeter
Perimeter measures length, or distance. It is always measured in regular units (feet, inches, meters, etc.).