Method #1 – Diagonal from the length of one side
Calculators
Formula – How to calculate the diagonal of a square from the length of one side
Length of the diagonal = √(L2 + L2)
Where “L” is the length of one side of the square.
Example
A square has a length of 10.
Length of the diagonal = √(102 + 102) = √(100 + 100) = √200 = 14.1421
Method #2 – Diagonal from the Area
Calculator
Formula – How to calculate the diagonal of a square from the area
Length of the diagonal = √(a + a)
Example
A square has an area of 100 inches2
Length of the diagonal = √(100 + 100) = √200 = 14.1421
Method #3 – Diagonal from the Perimeter
Calculator
Length of the diagonal = √(a + a)
Example
A square has an area of 100 inches2
Length of the diagonal = √(100 + 100) = √200 = 14.1421
… from the perimeter
Length of the diagonal = √((P ÷ 4)2 + (P ÷ 4)2)
Example
A square has a perimeter of 40.
Length of the diagonal = √((40 ÷ 4)2 + (40 ÷ 4)2)
Length of the diagonal = √(102 + 102)
Length of the diagonal = √(100 + 100)
Length of the diagonal = √200
Length of the diagonal = 14.1421