Potassium ferricyanide, potassium ferrocyanide, and their combination system are widely used redox probes for electrochemical impedance spectroscopy (EIS) characterization. In this work, electrochemical behavior of K₃Fe(CN)₆, K₄Fe(CN)₆, and K₃Fe(CN)₆/K₄Fe(CN)₆ redox probes at five different concentrations using a screen printed carbon electrode (SPCE) by cyclic voltammetry (CV) and EIS methods was analyzed. Redox potentials were observed as a result of anodic and cathodic peak with CV analysis with determination 10 mM appropriate concentration through 0.01 mM, 0.1 mM, 1 mM, and 100 mM. In addition, with EIS analysis, each redox probe was simulated according to two different Randles circuit models and fitting equivalent model with varying concentration was determined and examined in detail. The results also demonstrated that selected high and low concentrations of redox probes can be categorized in two different models, although 1 mM behaved as a critical transition concentration. This study may contribute to the determination of relevant redox probe and its concentration in electrochemical investigations by selecting K₃Fe(CN)₆/K₄Fe(CN)₆ to decrease any risk of inaccuracy.