Studies in the proton exchange membrane fuel cell (PEMFC) have evaluated different catalyst systems, using fixed mass percentages as the criterion to prepare catalyst layers. Some studies presented masses between 20 and 40% of ionomer in the catalyst layer as best composition; however, they also showed that any modification in the catalyst structure, such as support material or metal percentage, changes remarkably the membrane electrode assembly (MEA) performances. Thus, the volume of a catalyst used changes the amount of Nafion ionomer required to prepare catalyst layers with high efficiency. Consequently, to compare different catalysts in their highest performance conditions, it has become necessary to develop a volumetric criterion to calculate the quantity of Nafion ionomer necessary for each catalyst. In this work, the masses and the volumes of catalysts were compared to three other catalysts as the criterion to transpose the adjustment of the catalyst layer composition made to Pd/C 20%. The use of catalyst volume as the criterion to calculate the quantity of Nafion ionomer in the catalyst layer resulted in MEAs significantly more efficient than those prepared according to the fixed mass percentage. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.