The objective of this study is to develop a food security index that is consistent with five principles: boundedness, reliability, duplicability, applicability, and predictability. The index developed, called National Food Security Index (NFSI), is easy to interpret and comparable across time and among countries. The NFSI is composed of three components, physical availability, economic affordability, and market accessibility, and can be calculated in terms of calories as well as quantity. The NFSI measures a country’s capability of accessing the food it requires on a yearly basis. The index can be used to build early warning systems for individual countries.