The nucleus–nucleus reaction cross-sections of [Formula: see text]C and [Formula: see text]C at 240[Formula: see text]MeV/u are calculated using the optical limit of the Glauber model. The deformation and radii of a deformed Fermi density are calculated from the relativistic mean field (RMF). The results are compared with the recent experimental data. It is found that the Fermi density whose quadrupole deformation parameters and radii are derived from RMF, using TMA effective interaction in the RMF Lagrangian, provide a satisfactory explanation of the experimental data of Na isotopes, except for [Formula: see text]Na, which are expected to be strongly deformed. For F isotopes, the deformed Fermi density adjusted to the radii derived from RMF, using TMA interaction, presents a lower reaction cross-section. The Lagrangian parameters set NL3* gives a good description of the data which is better than that predicted by TMA. On the other hand, the two forces cannot describe the reaction cross-section of [Formula: see text]F since it is expected to have a deformed halo structure. The radius deduced from the data is found to be of the order 3.5[Formula: see text]fm.