The net dietary protein energy ratio (NDpE) is a measure of protein quality that expresses how much usable protein a food provides relative to its total energy content. It combines two things: the quantity of protein present and the quality of that protein, usually judged by its amino acid profile and digestibility. The “net” element adjusts for the fact that not all ingested protein is retained by the body. Foods with a high NDpE, such as eggs, milk, meat, and soy, deliver substantial usable protein per kilocalorie, which makes the ratio useful when planning diets where energy is restricted but protein needs remain high, for example in weight management or in treating protein-energy malnutrition. It remains a research and formulation tool rather than a consumer label metric.