A polarization test is the most commonly used method for diagnosing microbial fuel cell (MFC) performance. Reproducible measurement method and fair assessment are very important to draw significant information; however, they have not been conducted in the MFC field. For a reproducible polarization method and fair assessment of the MFC, diverse external resistance change (ERC) and linear sweep voltammetry (LSV) polarization methods were conducted using duplicate single chamber MFCs along with other routine tests in this study. The 3-hour optimum external resistance operation followed by the 2-hour open circuit time prevented power overshoots. When a faster polarization method is used, polarization results were more reproducible, whereas power and current densities increased and polarization and optimum resistances decreased. Because performance comparison is fair and valid when it comes to a same polarization method, interconversion factors among different polarization methods were generated by using our polarization data, which were accurately measured and verified. The interconversion factors were successfully applied to the real data sets. Operational maximum power densities were provided in this study because maximum power density from any polarization test is always overestimated. It was found that the higher coulombic and energy efficiencies were attributed to lower systematic internal resistance and high anode performance. It was also found that 90% of the total cell impedances were charge transfer impedance. Impedance and polarization tests show that the cathodic resistances were 2-3 time larger than the anodic resistances. Initial voltage drops and rise during the cell operation were related with the cathode performance deterioration.