Stray losses should be carefully considered in loss reduction studies, to increase efficiency of oil immersed transformers. These losses occur due to leakage fluxes and cause local hot-spots and overheating on the tank walls and other structural metal parts. In this study, obtaining an expression of suitable shunt dimensions which satisfactorily reduces the stray losses on tank walls, is aimed. 3D finite element method was intensively used in analyses and main results were also validated by experimental studies. A simple expression of shunt dimensions is proposed. To generalize this expression, obtained shunt dimensions are expressed by means of winding dimensions. Using this optimum shunt dimensions, tank wall losses and total short circuit losses were reduced by 91.43% and 14.9%, respectively.