Έγινε κατασκευή ενός προγράμματος το οποίο εξετάζει μια κατασκευή και υπολογίζει αναλυτικά τον κίνδυνο που αυτή διατρέχει λόγω κεραυνών. / The subject of this project is protection against lightning, meaning the measures needed to be taken for a building so that a possible lightning strike will not cause human or material damage. The first part consists of an essential theoretical approach on the lightning phenomenon. Both the causes, the consequences and the conditions in which the lightning occurs are being analyzed. Furthermore, the characteristics and the qualifications a Lightning Protection System needs to comply with, are given, according to the Greek standard ΔΛΟΣ 1197 and the European standard IEC 62305-2. The factors one examines to determine the risk, the technical details of the LPS, and the -step by step- calculation of the risk are being mentioned. After this analysis, the criteria whether the building is adequately protected, or not, are given, and in case the answer is negative, the procedure to design a safe LPS is given. Along with writing this essay, a computer program was produced. The program calculates the risk a building faces due to lightning. In the second part of the essay one can read the way this program works and the description of its construction. First, an algorithm approach of the procedure of risk calculation is given in detail. The program runs in Microsoft Excel and includes functions, menus, graphics and other special features. Given that the procedure was so complicated at some point, we had to use Visual Basic nested programming to produce a functional program. In the final part, significant parts of the code and some programming methods are described. The results this program gives, allow an engineer to have a good overview on the protection the lightning building provides, and to choose an effective, cost efficient LPS, if needed.