Perimeter is the distance around the outside of a shape. You measure it by adding up all the side lengths. The result is in regular units — centimetres, metres, inches.
Area is the amount of flat space inside a shape. The result is always in square units — cm², m², in². You multiply two lengths, so the unit gets squared too.
These two measurements are completely independent. A shape with a large perimeter can have a tiny area, and vice versa. A 1×9 rectangle and a 3×3 square both have perimeter 20, but their areas are 9 and 9… wait: 1×9 = 9, 3×3 = 9. Try 1×9 vs 5×5: perimeter 20 vs 20, area 9 vs 25. Same perimeter, very different areas.
Remember
Perimeter = around the outside (plain units). Area = space inside (square units). The ² in cm² is your reminder.
Real World
Fencing a garden uses perimeter — you're measuring around the edge. Laying turf uses area — you're covering the inside. Same garden, two different measurements.
Feeling ready?
Put this concept to work with a practice workout.