Electrochemical impedance spectroscopy (EIS) is an electrochemical surface characterization technique and has been widely used in biosensor and chemical sensors, also provides label free detection. This technique is used as faradaic and non-faradaic measurement. The advantage of the sensitivity of faradaic impedance spectroscopy becomes useful and preferred technique. In this review we tried to answer these questions: how Nyquist plots are fitted in proper circuit and how a proper circuit element is chosen in fitting and impedance calculation steps. Nyquist plot can become very confusing to fit on a proper circuit modal and calculation of impedance (Z). Z is called in other word as electron transfer resistance (R-et), additionally electrolyte interface impedance (R-s), capacitance (C) and Warburg impedance (W) are the other elements. These all circuit elements must be constructed in a proper order to fit Nyquist plot into a good circuit model. Therefore it is very important to examine Nyquist plot for accurate calculation. (C) 2014 Elsevier B.V. All rights reserved.