Abstract Effective atomic number acts as a fundamental property of compounds and mixtures and it plays a vital role in the computation of various dosimetric parameters such as buildup factor, effective dose and heat generation. Effective atomic numbers have been computed in the energy range from 1 keV to 100 GeV for different chemical compositions of calcium–strontium-borate glasses. The effective atomic number values have been computed and compared by two different methods ((a) ratio of atomic to electron cross-section and (b) logarithmic interpolation of molecular cross-section values). It has been observed that in the lower energy region, two interpolation regions occur for all the selected glasses, which results in two effective number values at the same energy. Hence, experimental verification of effective atomic number is required in the lower energy region.