Diagonal of a Square Calculator

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Choose which measurement you already have; the calculator solves for all others.
All length outputs are shown in this unit. Area is shown in the same unit squared.
The length of one side of the square.
Diagonal
7.071068

Corner-to-corner distance (d = a * sqrt(2))

Side length5
Perimeter20
Area25

Diagonal: 7.0711 m from a side of 5.0000 m.

  • The diagonal is always 1.4142 times the side length (approximately 1.4142 times).
  • A 5.0000 m side produces a diagonal of 7.0711 m, a perimeter of 20.0000 m, and an area of 25.0000 m^2.
  • The diagonal bisects the square into two congruent 45-45-90 right triangles, where the two legs are equal to the side and the hypotenuse is the diagonal.

Next stepIf you are squaring up a room or frame, measure both diagonals - they should be equal. A difference greater than a few millimetres indicates the corners are not at 90 degrees.

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