This paper focuses on the biodiesel density predictive models and examines the accuracy of the HCC methodology which bases on Rackett equation modified by Spencer and Danner to estimate the density of waste cooking oil (WCO) biodiesel in a wide range of temperature based on its fatty acid methyl ester components. The calculated results are compared with experimental measurements for the density aiming to validate the chosen method. The analysis results obtained show that this method does not, in all cases, yield high accuracy even though its use is simple. Particularly, in case of the biodiesel derived from waste cooking oil (WCO), this method is not accurate enough to predict its density with the deviations between experimental data and calculated density getting relatively high, around 3.4%