Enteric fermentation is estimated to be one of the largest sources of anthropogenic methane emissions in the United States. Although a range of approaches are currently used to estimate enteric emissions, methods vary in their degree of uncertainty and challenges remain when scaling from individual animals or farms to the national scale. At the request of multiple federal agencies, the National Academies of Sciences, Engineering, and Medicine convened a committee to evaluate methane measurement and monitoring approaches and opportunities to improve inventory development. The study focused on the predominant methane sources including enteric fermentation, manure management, oil and petroleum systems, landfills, and coalmines. For enteric fermentation specifically, the committee found that updating and simplifying the equations used in the development of the current US Greenhouse Gas Inventory (GHGI, which follows Tier 2 Intergovernmental Panel on Climate Change methodologies) based on synthesis of recent studies could improve emission estimates. Key uncertainties in existing emission estimates were found to be the result of limited availability of activity data for cattle numbers, feed intake, and feed composition, and emission factors adjusted by state or region that may be inaccurate on a local scale. Broadly, the committee recommended that the US establish and maintain a nationwide research effort to improve accuracy, reliability, and applicability of anthropogenic methane emissions estimates, accounting for all sources. This should include atmospheric measurements, regularly reviewed and updated “bottom-up” methodologies that are currently used in the GHGI, and the establishment of a fine scale, gridded inventory that can be verified using atmospheric observations.