 Using band theory, the electron density,formula_5 is number of electrons per unit volume in the conduction band.For holes, formula_8 is the number of holes per unit volume in the valence band.To calculate this number for electrons, we start with the idea that the total density of conduction-band electrons, formula_5, is just adding up the conduction electron density across the different energies in the band, from the bottom of the band formula_10 to the top of the band formula_11.