COMET-Farm is a web-based tool developed by Colorado State University in partnership with the Natural Resources Conservation Services (NRCS) of the US Department of Agriculture (NRCS-USDA) that employs outputs from DayCent and other models to estimate the change in soil carbon stock and GHG emissions impacts at the farm-scale. In addition, COMET-Farm allows users to evaluate alternative options to reduce GHG emissions and sequester carbon. The tool uses spatially explicit data on climate and soil conditions, which allows it to produce more site-specific estimates. This tool has been used to quantify emission reductions in the voluntary carbon market.