The study of biodegradation of chemicals that are discharged into water bodies is important to determine the risk to the environment that is associated with the chemical. The biodegradability of a chemical can be characterized by conventional oxidation parameters such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), and theoretical oxygen demand. Because the BOD5 estimation method takes five days, other methods have been sought for measuring oxygen requirements of a sample. One of them is the COD test which makes use of a strong oxidizing agent under acidic conditions. In this paper, a combination of BOD5 and COD experimental data is used to develop a quantitative model for the prediction of biodegradability. Furthermore, the criterion used to classify a substance as “readily biodegradable” is the one specified by the European Chemical Agency (EChA)’s CLP (Classification, Labeling, and Packaging) Regulation.