In our world today more and more people are carrying portable electronic devices, like smart phones, music player devices or cameras. For such a portable equipment piezoelectric energy harvester devices, due to their small sizes, can be a useful solution as they create energy while on the go making it possible to charge the battery. In my BSc final project I introduce piezoelectric beam energy harvesters. A short overview about the mathematical background is given in the first part of the project. It helps to understand the calculator software, what I developed in MATLAB, to simulate the time function of the generated output voltage of a piezoelectric beam for different excitation signals. The second part of the project presents the calculator. A short user manual is written for the calculator so anybody can use it easily. It shows how to initialize the program properly by setting the material properties, the sampling frequency and the excitation signals. In the third part of my final project the simulation results is presented for different conditions. The voltage production of the piezoelectric beam was simulated for several external vibration excitations (Sine, Cosine, Impulse, Square Wave, Sawtooth and random signal) at different frequencies. Based on the simulation results the working point to obtain the maximum amount of power can be determined. To verify my results, later on I would like to compare the simulation results with real test results. So far, in my final project I present the 3D CAD model of two possible measurement arrangements, which can be used later on and where to use the bimorph cantilever piezoelectric energy harvesters.