In a simple cubic lattice the atoms are located only at the corners of the cube.

Let us assume the edge length or the side of the cube = a

And the radius of each particle = r

The relation between radius and edge a

Can be given as a = 2r

The volume of the cubic unit cell = side³ = a³

= (2r³)

= 8r³

Number of atoms in unit cell

The volume of the occupied space

And we know that, the packing efficiency

= 52.36%