This paper describes simple theoretical calculations of the overall heat release rate (HRR) of multiple objects at both constant and varying distances that have been carried out. The results were compared to both fire experiments in a longitudinal ventilated model tunnel (scale 1:15) using piles of wooden pallets placed at varying distance from each other and with model scale fire experiments (scale 1:4) conducted with piles of wooden pallets in the open. Two different methods are presented which are based on physical relations for fire spread between the piles of wooden pallets. The first method uses a critical heat flux as ignition criteria while the other method uses an ignition temperature. The method using the critical heat flux as ignition criteria shows very good agreement with the corresponding experimental results used. The method using the ignition temperature as ignition criteria did not agree well with the corresponding experimental results. The prerequisite that the burning objects should not necessarily have to be positioned at equal distances was fulfilled. The results can be used to estimate the heat release rate in full scale tunnel experiments where wooden pallets have been used as fuel.