Livestock products require more land unit output than do foods made directly from plants. Consequently, the combination of global population growth and shifts toward more affluent diets places increasing pressure on agricultural land resources. However, the impact of dietary shifts on food production capacity is not straightforward because livestock feed requirements vary widely across classes and because grazing and some forage production does not necessarily compete with use of land for food crops. These nuances leave vast room for misinterpretation and misinformation regarding the capacity of land to support food production and the impact of livestock production on food security. To this end, we present a methodology for estimating the land requirements for the major livestock classes in the U.S.: beef, chicken, pork, dairy, and eggs. A spreadsheet model was used to determine the feed requirements and corresponding land needs of production animals and the supporting livestock. Data from peer-reviewed literature, government reports, and industry publications were used to populate the model. We report the feed needs and land requirements per unit of food output, expressed per kilogram of product, per kilocalorie, and per gram of protein. In addition, we compare these results to other estimations in the literature. Finally, we validate the model by calculating the feed needs of the current U.S. livestock inventory against actual disappearance of feed products. This model provides a systematic and transparent approach to determining the feed and land requirements of livestock.