LaserCalc is a tool to calculate optical paths and resonators based on Gaussian beam matrix optics. Optical elements such as lenses or distances can be set up to an optical path. An input beam parameter (z & w value) as well as the wavelength can be set. The programm calculates the propagation of the beam along the path. For an optical resonator, the TEM00 Eigenmode of a given wavelength is automatically calculated. Furthermore, a stability parameter is derived.