Alkyl peroxy radicals, RO₂, are important intermediates in the oxidation of organic material in the atmosphere. It was shown earlier that hydrogen atom migration within RO₂ can be important and results in the formation of additional oxidants and large highly oxygenated molecules that lead to more and larger aerosols. In this work we propose a method for predicting the chemical rate for these H migrations in RO₂, helping atmospheric models to correctly include these reactions.