The metal loading of supported metal catalysts is often assumed to be equal to the designed or nominal value. However, this is often not the case. Although the focus of this paper is on supported noble metal catalysts prepared by the sol-gel method, discrepancies in actual metal loadings may also occur with catalysts prepared by traditional methods such as impregnation or ion exchange. Metal may be lost during catalyst preparation, drying, or pretreatment. For this reason, it is essential to measure the actual metal loading before proceeding with further analysis of catalytic properties.