Given the fact that human activities currently emit greenhouse gases (GHG) equivalent to over 40 billion tonnes of CO₂ yr^-1 and that approximately 30% come from agriculture, land use and land use change, natural resource management (NRM) and sustainable land management (SLM) activities could have a large role to play in climate change mitigation. The types of land management activities covered by such projects vary widely and these activities have different C and GHG impacts. The Carbon Benefits Project (CBP) has built a comprehensive, standardized system for Global Environmental Facility (GEF) and sustainable land management (SLM) projects funded by other sources to measure, monitor and model carbon stock changes and greenhouse gas (GHG) emissions associated with land uses such as forestry, annual and perennial crops, agroforestry, silvopasture, livestock, settlements and wetlands.  The system was designed for projects varying in size from tens of square kilometres to tens of thousands of square kilometres. The CBP builds on existing GHG inventory tools, of different complexity, developed over the past 15 years at Colorado State University. We will demonstrate aspects of this new modular, web-based system which allows users to collate, store, analyze, project and report net C stock changes and GHG flux for baseline and project scenarios in SLM interventions. Existing SLM projects in Brazil, China, Kenya and the transboundary area between Niger and Nigeria are being used as test cases.  The toolkit may be accessed at http://cbp.nrel.colostate.edu.