A new method for calculating proton induced SEU (p-SEU) rates in orbit from heavy ion cross section data is presented. It is based on a simple expression to derive the p-SEU cross section fi-om the heavy ion results which leads to an 'effective LET flux' for the protons in the given orbit. The resulted p-SEU rates are in good agreement with those calculated from measured p-SEU cross section data. A comparison with other empirical models is given.