A computer-implemented method and system of modeling physical properties of biodiesel feedstock are presented. The invention method and system include (i) estimating values of a physical property of constituent fatty acid fragments of a mono-, di-, or triglyceride, and (ii) computing a value of the physical property of the mono-, di-, or triglyceride by expressing the value of the physical property of the mono-, di-, or triglyceride as a sum of the estimated values of the physical property of constituent fatty acid fragments thereof. The method and system further include repeating steps (i) and (ii) for different mono-, di-, and/or triglycerides, resulting in a plurality of computed values of the physical property of different mono-, di-, and triglycerides. The determined value of the subject physical property enables blending of the biodiesel feedstock in production of biodiesel.