We investigate the calculation of the magnetic form factors of nano-objects with complex geometrical shapes and non homogeneous magnetization distributions. We describe a numerical procedure which allows to calculate the 3D magnetic form factor of nano-objects from realistic magnetization distributions obtained by micromagnetic calculations. This is illustrated in the canonical cases of spheres, rods and platelets. This work is a ?rst step towards a 3D vectorial reconstruction of the magnetization at the nanometric scale using neutron scattering techniques. ; Comment: 7 pages, 5 figures. To appear in Physics Procedia