Calcium is an essential nutrient generally obtained from dietary foods. However, its metabolism is a complex biological network requiring an effective analytical tool. In this review, a few notable calcium mechanistic models are assessed, emphasizing the power of mechanistic modeling in analyzing biological systems because no publication has reviewed them in a single place. Reviewed models are categorized by target systems: calcium absorption, calcium excretion, bone turnover, and whole calcium homeostasis. In the calcium absorption model, two transport systems carrying calcium from intestine to blood have been mechanistically described. Since urine calcium excretion is poorly understood, its model has not been explicitly developed although it is modeled as a part of the whole calcium metabolic system. Cell-based bone turnover model has been conceived to describe the mechanism under bone cell regulation. Finally, whole calcium metabolism has been a target to explain the metabolic control of calcium homeostasis that is linked to the endocrine system. Reviewed models focus on explaining how the calcium metabolic system behaves in response to conditional perturbations by involving effective factors such as endocrine system. We expect that not only will this study provide comprehensive information for future studies in calcium metabolism, but also that it will suggest what the concepts of biosystem modeling are and how they can be used for assessing the target system.