What potentials do manufacturing companies have for identifying inefficiencies in their use of resources? Assessing the products with regard to their durability, functional usefulness, use of materials, etc. is only one aspect of the exercise. The actual production operations and the search for in-plant inefficiencies represent the other. In Germany, the material flow cost accounting (MFCA) method was developed years ago to tackle this requirement. It evaluates material losses in the company in monetary terms and thus points up the economic benefit of resource efficiency. MFCA first achieved practical relevance and large-scale application in Japan. Now there is even an ISO standard on the method. The article outlines the process and presents typical examples. It explains how a methodological bridge can be built to assess the loss of material in ecological terms too.