[en] In order to estimate single event upset (SEU) rates in low orbits of a certain device one needs both its heavy ion cross section as a function of LET (linear energy transfer) and proton cross-section as a function of proton energy. These 2 curves can be measured only in separate accelerators. To save costs many models were developed to derive one cross-section from the other one. In this paper we present a new method, requiring no adjusting parameters, that gives p-SEU cross-sections from heavy ion cross-sections. This method is based on the semi-empirical model. The resulted p-SEU rates are in good agreement with those calculated from proton SEU cross-section data. A comparison with other empirical models is given