Mathematical models are essential for integrating different processes that control rates of soil carbon dynamics and for assessing carbon sequestration and the related climate benefits. Many models have been proposed in the literature, with no overall consensus on the best model that can provide relevant insights at a large range of scales and for multiple questions. This chapter reviews general groups of models with their expected ranges of application. It also reviews recent advances in using models of any level of detail to compute carbon sequestration, and the climate benefit of carbon sequestration. Using agricultural soils from Sweden and Hawai'i as examples, the chapter shows that new carbon inputs to the soil do not remain for long timescales, and only small proportions are stabilized. Although soils are a promising reservoir to store carbon, long timescales are required to store amounts of carbon of relevance to mitigate climate change.