Hydraulic conductivity can be obtained from the dielectric constant by using previously suggested models. However, many input parameters have to be applied to the models. The objective of this study is to investigate the error norm of each parameter, which is an essential value to obtain the hydraulic conductivity. The theoretical relationships between the dielectric constant and hydraulic conductivity are addressed, and the equations are arranged in terms of the hydraulic conductivity. To obtain the dielectric constant and other parameters, a laboratory test was performed, and glass beads, Jumunjin sand, and field sand were used to determine the sensitivities of each equation through particle size distributions. The constant water head test was conducted to assess the hydraulic conductivity as a reference value, and the dielectric constant was also measured by using attached electrodes in the constant water head test under the same experimental conditions. Through an analysis of the measured data, we found that the voltages between the first and the second reflections and the converged voltage had a strong influence on the theoretical equations. Moreover, care is necessary when obtaining the two voltages to determine the hydraulic conductivity reliably through the dielectric constant.