A method is proposed for the calculation of the range profile of ions implanted into a double layer substrate. Results of calculation for the case of boron implantation into silicon through silicon dioxide are presented. In the present method one first considers the situation obtaining if the silicon beneath the interface were replaced by oxide. The profile is then known from standard data. A computer program then optimizes summation of Gaussians to obtain the energy distribution of equivalent ions normally incident at the interface. This distribution is then used to calculate the range profile in the real case of silicon beneath the interface again using standard data. The assumption in this is that the energy distribution of equivalent ions normally incident at the interface is independent of the underlying material.