Soil carbon sequestration can be estimated from field to global scale using numerical soil/ecosystem models. In this chapter, we describe the structure and development of models that have been widely used at international level, from simple models that include carbon only to models that include descriptions of the dynamics of a range of nutrients. We also present examples of the application from field to global scale of different models to answer a range of different questions on the impact of land use and climate changes on soil carbon sequestration. A full discussion of the impact of soil carbon modeling on political and socioeconomical aspects is included to emphasize the need of a close interaction between model developers, researchers, land owners/users and policy makers to ensure the development of robust approaches to climate change, food security and soil protection. Whatever type of models are used to meet future challenges, it is important that they continue to be tested using appropriate data, and that they are used in regions and for land uses where they have been developed and validated.