Cloud points of aqueous poly(propylene glycol) (PPG) mixtures at various concentrations of PPG are determined using the particle counting method. The average molecular weight of the PPG is 1205 g.mol(-1), and its concentrations are changed from 0.01 up to 0.15 mass fraction. In this method, by slowly increasing the solution temperature, the number of particles is measured. At the temperature where a new phase appears, a sudden change in the number of particles would be observed, and this temperature indicates the cloud point for the solution. This procedure is repeated for various PPG concentration mixtures, and the cloud-point curve of the aqueous PPG mixture is determined. Also, a simple model for correlating cloud-point data is presented, and the results show a good consistency between the measured and the calculated data.