The insertion loss of louvered terminations positioned at the end of a rectangular duct is determined using acoustic finite element analysis. Insertion loss was determined by taking the difference between the sound power with and without the louvers at the termination. Analyses were conducted in the plane wave regime and the acoustic source was anechoic eliminating any reflections from the source. The effect of different louver configurations on insertion loss was examined. Parameters investigated included louver length, angle, and spacing between louvers. Based on the analyses, equations were developed for the insertion loss of unlined louvers.