Graphite intercalation compounds (GICs) are formed by inserting various atoms and molecules between the layers of graphite. Among these GICs, five structures have been reported wherein a single atom M was intercalated into graphite with chemical formulae MC6 and MC8 and different stacking orders. The formation energies of the GICs with these crystal structures and various intercalants (M) were investigated using first-principles calculation. Consequently, the formation energies of all the GICs reported to be synthesized were negative, indicating a good agreement with the experimental results. Our study also provides insights into the relative stability required for synthesizing GICs. Furthermore, we determined the negative formation energies of GICs for M =Sc, Y, Fr, and Ra, which are yet to be reported.