Internal conversion is favored whenever the energy available for a gamma transition is small, and it is also the primary mode of de-excitation for 0→0 (i.e. E0) transitions. The 0→0 transitions occur where an excited nucleus has zero-spin and positive parity, and decays to a ground state which also has zero-spin and positive parity (such as all nuclides with even number of protons and neutrons). In such cases, de-excitation cannot take place by emission of a gamma ray, since this would violate conservation of angular momentum, hence other mechanisms like IC predominate. This also shows that internal conversion (contrary to its name) is not a two-step process where a gamma ray would be first emitted and then converted.
The competition between IC and gamma decay is quantified in the form of the internal conversion coefficient which is defined as  where  is the rate of conversion electrons and  is the rate of gamma-ray emission observed from a decaying nucleus. For example, in the decay of the excited state at 35 keV of Te (which is produced by the decay of I), 7% of decays emit energy as a gamma ray, while 93% release energy as conversion electrons. Therefore, this excited state of  has an IC coefficient of .
For increasing atomic number (Z) and decreasing gamma-ray energy, IC coefficients increase. For example, calculated IC coefficients for electric dipole (E1) transitions, for Z = 40, 60, and 80, are shown in the figure.
The energy of the emitted gamma ray is a precise measure of the difference in energy between the excited states of the decaying nucleus. In the case of conversion electrons, the binding energy must also be taken into account: The energy of a conversion electron is given as , where  and  are the energies of the nucleus in its initial and final states, respectively, while  is the binding energy of the electron.