A linear universal decay formula is presented starting from the microscopic mechanism of the charged-particle emission. It relates the half-lives of monopole radioactive decays with the $Q$-values of the outgoing particles as well as the masses and c
harges of the nuclei involved in the decay. This relation is found to be a generalization of the Geiger-Nuttall law in $alpha$ radioactivity and explains well all known cluster decays. Predictions on the most likely emissions of various clusters are presented.
