Mercury is a developmental neurotoxicant, ubiquitous in the environment, existing both naturally and through anthropogenic additions, resulting in human and ecological exposure risks primarily via consumption of mercury contaminated fish tissue. To better understand the risk associated with mercury exposure, it has become necessary to not only understand the mercury biogeochemical cycling within water bodies where typical mercury exposure occurs, but to also understand terrestrial mercury biogeochemical cycling, including mercury deposition, transformation, and transport to receiving water bodies. Here, we present a relatively straight-forward and transparent spreadsheet-based pilot model to simulate the biogeochemical cycling of mercury in watersheds.