This video illustrates the calculations of the linear and planar densities of a Face Centered Cubic (FCC) unit cell. Linear density is the number of atomic radii per line length in a particular crystallographic direction. Planar density is the atomic area per plane area where the plane must pass through an atom’s center for that particular atom to be included. The calculations of linear density for [100], [110] and [111] directions and planar density for (100), (110) and (111) planes are shown.