This paper describes a comprehensive analysis of the geometrical parameters influencing the sensitivity of a coplanar electrode layout for electrical impedance flow cytometry. The designs presented in this work have been simulated, fabricated, and tested. 3D finite element method was applied to simulate and improve the sensitivity of the coplanar designs for two spacings between electrodes. The proposed model uses conditional expressions to define spatially dependent material properties. The vertical and lateral sensitivities were evaluated for all the designs. The experimental results obtained with polystyrene beads show good agreement with the simulations. Precentering particles with dielectrophoresis allowed to control their position in the microchannel. The optimized designs are envisioned to be used for sizing and characterizing particles from single cells to cell aggregates.