Through this thesis an application for impedance matching with one stub is described. The input values are: load impedance ZL, characteristic impedance of the transmission line Z0 and the frequency f at which the matching must be performed. The mathematical model describes a process which of the following input values comes to the distance of the stub from the load d and stub length l, which are necessary for impedance matching. PHP is mostly used for this calculation. In addition to solutions from the mathematical calculations, two schemes are displayed and the graph of the magnitude of the reflection coecient is plotted against the frequency. Displaying of the particular scheme is based on whether the stub is parallel or serial and terminated by a short or by an open circuit. For searching the reflection coeficient, it required a lot of calculations with complex numbers, which is why javascript library Math.js was included. To draw a graph library, d3.js was used. This application should be helpful to people who work in radiocomunications and similar branches and it should also help students. Because of the long and demanding calculation which would take a long time if done by hand, this application will do evertything in a few clicks. Fast calculation, combined with schemes and graphs, gives a better picture which is easier to understand and is ultimately helpful.