Perimeter of a Square Calculator

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Choose which measurement you already know. The calculator solves the rest.
The unit for every length and area shown. The shape is the same in any unit, so this only changes the labels.
The length of one side of the square.
Perimeter
20m

Total boundary length of the square (4 times the side length)

Side length5m
Diagonal7.0711m
Area25m²

Perimeter of this square: 20.0000 m

  • The side length is 5.0000 m, so the perimeter is 4 times that: 20.0000 m.
  • The diagonal from corner to corner is 7.0711 m (the side times the square root of 2, approximately 1.4142).
  • The total interior area is 25.0000 m².
  • For a square of this size, the perimeter-to-area ratio is 4.0000 per m - squares have the smallest perimeter for their area of any rectangle.

Next stepIf you are buying fencing or framing, add an allowance for corners, overlaps or waste. A common rule of thumb is to add 5 to 10 percent to the calculated perimeter.

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