Tools are needed to evaluate and compare different available feedstocks, and process parameters andmodifications for biodiesel production. To address this need, a biodiesel process model was developed with commonly usedspreadsheet software and process-engineering principles. The basis of the model is a continuous process with two stirred-tankreactors and sodium methoxide catalysis. The process was modeled as 27 units with 51 flows and 18 components. Mass flowrates and compositions of the process input and output streams were quantified using mass and component balances, energybalances, stoichiometric relations, and established process parameters. Oil composition and rate, methanol:triglycerideratio, and expected transesterification of triglyceride were the user-specified inputs in the model. Based on commonlyreported parameters (6:1 methanol:triglyceride ratio and 98% transesterification) and a basis of 100 kg/h crude soybean oil,the model computes (in kg/h) inputs of 13.8, 10.8, 34.7 for methanol, 10% sodium methoxide in methanol, and process water,respectively, and outputs of 93.5, 10.3, 55.6 for soy biodiesel, glycerol, and waste stream, respectively. These mass flow ratescan be linked to cost data for calculating the material costs from various feedstocks, and can be readily adapted to factorin alternative parameters and units.