This master´s thesis presents the evaluation of several loudness calculation algorithms. Two of the algorithms are published standards: Replay Gain and ITU-R BS. 1770, and the others are modifications of these two. To evaluate the algorithms, a loudness listening experiment was realized. In the experiment audio files containing speech and pop music were used. The audio files and the corresponding subjective loudness values retrieved from the experiment were used to evaluate the algorithms. The precision of the algorithms was also tested using a subjective loudness database from IRT (Institut für Rundfunktechnik). In both evaluations, ITU-R BS. 1770 produced lower errors than the Replay Gain algorithm, when compared to the subjective loudness values. Of the modified algorithms, the ITU based algorithms that included a gate function produced the best result.