The AvaSoft-Thinfilm by Avantes is a calculation software designed for controlling system and conducting measurements on the thin film coatings. The software measures the the layer thickness coming from the reflection interference spectrum in optically transparent layers which are known as optical parameters. There are two methods used in calculating the films, these are Fast Fourier Transform (FFT) and Best Fit Optimization algorithm. The FFT method uses frequency of the interference pattern which are usually used in thick layers. On the other hand, the match spectrum optimization uses variation of thickness calculations. Also, the whole software comes with an extensive database of optical constant the n and k which are used as substrates and coatings. The database comprises of substrate and coatings which are important to specific applications.