In the present work, a new method is proposed for the measurement of the ice packing factor (IPF) of an ice slurry using the index of refraction. The purpose of the new method is to improve the resolution of the measurement and to increase its resistance to electric noise as compared to the standard IPF measurement technique that relies on the measurement of the freezing temperature. These two methods are similar in that they both obtain a concentration of aqueous solution from the measured physical quantities and calculate the IPF using the relationship between concentration and IPF. Both methods were also compared with the results from the calorimeter method obtaining the IPF directly. The two methods are in good agreement (within 5%), which demonstrate the validity of the newly proposed method.