Skip to story
ELI5 Yahaaa

The fence and the field

How Are Area and Perimeter Different?

Perimeter measures the walk around the edge; area measures the space inside.

Perimeter The fence around thefieldArea The grass inside it
One is the fence. The other is the field.

  1. Step 1 of 5

    Perimeter is simply the walk around the edge.

    1 Start at acorner2 Follow everyside3=Add the sidestogether

    Set off at one corner, follow every side back to where you started, and add up the distance. That total is the perimeter.

  2. Step 2 of 5

    It is a length, so the units are plain.

    Perimeter — metresa distancewalkedArea — square metressquares covered

    You are measuring a distance, so the answer is in metres, not square metres. Nothing is being covered, only walked along.

  3. Step 3 of 5

    Same perimeter, wildly different areas.

    Both need 16 mof fenceOne holds 15square metresThe other only7

    A long thin rectangle and a near-square can need identical fencing yet hold very different amounts of space inside them.

  4. Step 4 of 5

    The squarer the shape, the more it holds.

    1 m by 7 mlong and thin2 m by 6 mgetting squarer4 m by 4 ma square, thebest

    For a fixed amount of fence, area grows as the shape gets closer to square, and a circle does better still than any rectangle.

  5. Step 5 of 5

    Which one matters depends on the job.

    Buying fence Perimeter decides thecostBuying turf Area decides the cost

    Fencing a field, framing a picture or edging a lawn are perimeter jobs. Turf, paint and carpet are area jobs.

    Of all shapes with the same perimeter, a circle encloses the most area — which is why bubbles and pipes are round.

The short version

Perimeter is the distance around the edge and area is the space inside, and shapes with equal perimeters can hold very different areas.

Try it yourself

Make a 16-piece loop of string into a long thin rectangle, then a square. Same string, but the square clearly holds more space.

Topics

Next tiny story