This paper presents the estimation of water percolation threshold (phi(c)) of a nonionic microemulsion by studying its conductivity (sigma) as a function of water volume fraction (phi). The initial solution of alkyl polyglycosides/glyceryl monooleate/n-octane/isopropyl alcohol with weight ratios of 3/3/2/2 was diluted by brine (1 wt % sodium chroride), and the electrical conductance was measured along the specific dilution line. One factor design (OFD), which is an approach embedded in Design of Experiments (DOE), was used to model the variation of d(log sigma)/d phi with phi. A quadratic equation with natural logarithm transformation was then fitted and validated. The model was optimized to predict phi(c), the water volume fraction at which d(log sigma)/d phi is a maximum. The predicted value of 0, from the optimization of the model is 0.1245. In addition, fitting to the scaling law was conducted, and the value of phi(c) from this theoretical model was 0.1212. Apparently, these values are in excellent agreement. It is concluded that DOE can be used to estimate the value of phi(c) for a microemulsion relatively precisely with less computation and restriction compared to the conventional fitting approach.