The volume of foams used in packaging is enormous. Proper design requires identification of the correct material and selection of the correct density for each particular application. The vast amount of data in the literature is in need of a systematic analysis and a compact presentation. In this paper, the energy-absorption data of each class of cellular materials (such as open-cell elastic foams) are normalized and presented in a single diagram. Diagrams of this type are termed packaging-selection diagrams, and the optimal density of a cellular material can be obtained from them once the maximum permitted stress of the packaging is known. This new approach offers greater generality and simplicity than existing methods, such as the Janssen factor or energy-absorption diagrams.