This paper presents a software tool for load management in distribution transformers. This software application has three components, the first one emulates the electronic system, the second one makes data acquisition and the third one is an Excel sheet. In this case, the Excel sheet is the main component, which allows to estimate the transformer operation state (overload, sub load, nominal), core and coil losses and gives useful information for selection of distribution transformers based on economic criteria, using daily load curves obtained from measurements in transformers.