We have formulated a simple semi-empirical formulae for photon energy absorption buildup factors in the energy region 0.015-15 MeV, atomic number range 1≤Z≤92 and for mean free path up to 40 mfp. The results produced by the present formulae agree well with the data available in the literature. This semi-empirical formula may be extended to any compounds/mixtures/biological samples. This semi-empirical formula finds importance in the calculations of buildup factors of any materials which are required for radiation shielding, nuclear engineering, radiotherapy and nuclear medicine.

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