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Diagonal Calculator

Given:

Shorter Side (I)

cm ▾

Longer side (w)

cm ▾

trianle details image

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Diagonal Calculator for Rectangle

The diagonal calculator helps you find the diagonal, area, perimeter, and diagonal angles of a rectangle. Simply enter any two known values (length & width, area & one side, or perimeter & one side) to calculate the diagonal and other properties.

Diagonal of a Rectangle

A rectangle is a four-sided shape with all right angles (90°). Opposite sides are equal and parallel, while adjacent sides may differ. The diagonals of a rectangle are equal in length and intersect at its center.

Diagonal of a Rectangle

Formula for Diagonal

You can calculate the diagonal using the Pythagorean theorem:

Diagonal: D = √(l² + w²)

l = Length of the rectangle
w = Width of the rectangle

Other Rectangle Measurements

Area: A = l × w

Perimeter: P = 2(l + w) = 2l + 2w

How to Find the Diagonal of a Rectangle?

Finding Diagonal Using Area or Perimeter

Given Area & Length: w = A / l, P = 2(l + w), D = √(l² + w²)
Given Area & Width: l = A / w, P = 2(l + w), D = √(l² + w²)
Given Perimeter & Length: w = (P - 2l) / 2, A = l × w, D = √(l² + w²)
Given Perimeter & Width: l = (P - 2w) / 2, A = l × w, D = √(l² + w²)

Practical Example

Calculate the diagonal, area, and perimeter of a rectangle with length = 4 units and width = 3 units:

Length, l = 4 units
Width, w = 3 units
Diagonal, D = √(l² + w²) = √(4² + 3²) = √(16 + 9) = √25 = 5 units
Area, A = l × w = 4 × 3 = 12 units²
Perimeter, P = 2(l + w) = 2(4 + 3) = 14 units

How to Use the Diagonal Calculator

Input: Enter any two known values (length & width, area & one side, or perimeter & one side) and click calculate.

Output:

Diagonal of the rectangle
Area of the rectangle
Perimeter of the rectangle
Circumcircle of the rectangle
Diagonal angle of the rectangle

References

From Wikipedia: Circumscribed Circles

From WikiHow: Diagonal, Length, and Width

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