A cube can have 6 diagonals for the six faces and two main diagonals passing through its center. The diagonal of a cube can be calculated using the length of the edge of a cube, which is the length of its face, since its sides are squares. A cube is the only hexahedron. This page provides you with the Diagonal of a cube formula to calculate the diagonal of a cube using the edge of the cube. You can substitute the edge value in various units such as cm, mm, dm etc.
According to the above Diagonal of a cube formula, the square root of three times the measurement of edge gives the diagonal.