A 3D computer model has been developed for predicting magnetic fields in order to comply with legislation concerning safety and environment issues. The developed software, named “EMF-CS”, allows the user to predict and simulate magnetic fields generated by electrical MV/LV substations whose magnetic field emission has to be evaluated inside the plant as well as in surrounding areas. The model allows the positioning of different electrical components, such as MV cells, bus bars and cables, LV cables and switches, and the whole plant can be shown with 2D/3D views. Once the model has been created, the software automatically makes a test of the electrical scheme, checking the agreement among data/equipment involved. The outcome can be represented numerically (charts) or graphically (profiles or isolines) and can be exported as a spreadsheet, ASCII or graphical format. The model has been applied to an Italian standard MV/LV substation supplied by a synthetic circuit in order to simulate a rated and stable power condition. Comparison between measurements and predictions outside the substation shows a good agreement. A significant overestimation is shown only near MV cells probably due to the metallic enclosure which shields the magnetic fields generated by MV circuits.