This paper describes a software tool developed for estimation of the field moisture content of subgrade materials. Subgrade behavior is directly related to its moisture content. Unfortunately, some approaches of estimating field moisture content are too complex to be used in routine design. In this paper, the authors attempt to provide an approach that is easy to use. The software presented here was developed using expert system approaches. It is capable of analyzing data entered by the users, and providing estimations to meet different scenarios. The information entered by the user is first examined for its reasonableness and accuracy. Then, proper estimation models, of which there are many integrated into the system, and data searching processes are initiated. All results are evaluated based on how well the data is meeting the limitations existing during the model's original development. In the end, engineers can estimate the field moisture content based on the most appropriate descriptions of the site.