The inventive metric tool estimates the entropy of the source code as a measure of the complexity of the software. The tool considers the dependency of the symbols in the software. The tool constructs a data graph representing the structure of the program. Each symbol is shown as a node in the graph, with the dependencies shown as edges connecting the different nodes. The tool uses information theory to estimate the amount of information, or entropy, needed to describe those dependencies. The entropy provides a measure of the complexity of the program, as the greater the entropy, the more complex the dependencies, and the more complex the program.