The fence and the field
How Are Area and Perimeter Different?
Perimeter measures the walk around the edge; area measures the space inside.
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Step 1 of 5
Perimeter is simply the walk around the edge.
Set off at one corner, follow every side back to where you started, and add up the distance. That total is the perimeter.
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Step 2 of 5
It is a length, so the units are plain.
You are measuring a distance, so the answer is in metres, not square metres. Nothing is being covered, only walked along.
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Step 3 of 5
Same perimeter, wildly different areas.
A long thin rectangle and a near-square can need identical fencing yet hold very different amounts of space inside them.
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Step 4 of 5
The squarer the shape, the more it holds.
For a fixed amount of fence, area grows as the shape gets closer to square, and a circle does better still than any rectangle.
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Step 5 of 5
Which one matters depends on the job.
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
One is a length in plain metres, the other a count of squares — and the same fence can enclose wildly different amounts of field, because area grows as the shape squares up, with a circle beating every rectangle there is.
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.