A mathematical model of a tubular solid oxide fuel cell is presented. The complete electrochemical and thermal factors are accounted for in a rigorous manner. All required parameters are determined from independent sources; none are fit from performance data. To verify the accuracy of the model predictions, comparison is made with single cell test data from Westinghouse. Agreement with electrochemical and thermal results are within 5%, and for most points, much better. Predictions are shown for power-voltage, irreversibilities, and temperature and current distributions under various conditions.