Diagonal Paralelepípedo

D = √(a²+b²+c²).
Created by
Renato Passos, Eng. de Software
Reviewed by
Renato Passos, Eng. de Software

Last updated: Apr 18, 2026

D
13,0000

Formula

D = √(a²+b²+c²)

About this calculator

This calculator determines the length of the space diagonal of a right rectangular parallelepiped, also known as a rectangular prism or cuboid. The space diagonal is the straight line connecting two opposite vertices, passing through the interior of the solid. The formula used is D = √(a² + b² + c²), where a, b, and c are the lengths of the three edges meeting at a vertex (length, width, and height). The result is given in the same unit as the edges.

To use the calculator, enter the values of a, b, and c (in meters, centimeters, etc.) and click 'Calculate'. The calculation is based on the Pythagorean theorem applied in two steps: first, the diagonal of the base is computed (√(a²+b²)), then combined with the height (c) to obtain the space diagonal. This method is valid only for right rectangular parallelepipeds, where all faces are rectangles and angles are right angles.

This tool is useful in various practical situations, such as civil engineering to calculate the distance between opposite corners of a room or container, logistics to determine the maximum size of objects that fit in a rectangular box, and furniture design to check if a piece fits in a three-dimensional space. It is also applied in school geometry problems and packaging calculations.

Important precautions: ensure that all edges are in the same unit of measurement before calculating. The formula only applies to right rectangular parallelepipeds (with right angles). For oblique parallelepipeds, the diagonal is different. Also, the space diagonal should not be confused with the face diagonal, which is calculated separately (e.g., √(a²+b²) for the base face).

Frequently asked questions

What is the diagonal of a parallelepiped?

It is the longest distance between two opposite vertices of the solid, measured internally. Also called the space diagonal.

Does the calculator work for any type of parallelepiped?

No, only for right rectangular parallelepipeds, where all faces are rectangles and angles are 90 degrees.

Can I use different units for a, b, and c?

No, all edges must be in the same unit (e.g., meters, centimeters) for the result to be consistent.

What is the difference between a face diagonal and the space diagonal?

The face diagonal lies on a single face (e.g., √(a²+b²)), while the space diagonal goes through the interior of the solid.

How is the formula derived?

The Pythagorean theorem is applied twice: first on the base (√(a²+b²)) and then combining that result with the height (c).

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