In this paper, we present a software tool that helps the designer to analyze finite wordlength effects in digital filter implementations. The software tool is implemented in the MATLAB environment. For a given discrete transfer function, the various implementation structures can be analyzed in terms of existence of overflow oscillations, roundoff error gain and coefficient sensitivity. The main features of the package are described and applied to narrow-band IIR filters. These examples demonstrate the usefulness of the software package in exploring the performance of different structures due to finite wordlength implementations of digital filters.