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We have succesfully formulated the semi-empirical formula for α -decay half-lives of heavy and superheavy nuclei for different isotopes of the wide atomic-number range 94 < Z < 136. We have considered 2627 isotopes of heavy and superheavy nuclei for the fitting. The value produced by the present formula is compared with that of experiments and other eleven models, i.e. ImSahu, Sahu, Royer10, VS2, UNIV2, SemFIS2, WKB. Sahu16, Densov, VSS and Royer formula. This formula is exclusively for heavy and superheavy nuclei. α -decay is one of the dominant decay mode of superheavy nucleus. By identifying the α -decay mode superheavy nuclei can be detected. This formula helps in predicting the α -decay chains of superheavy nuclei.