Abstract: The osmotic coefficient (ϕ) reflects the degree to which the solvent in an electrolyte solution deviates from ideal solution behavior. The osmotic coefficient can be determined by various methods such as the vapor pressure method and the electromotive force method. The U.S. National Bureau of Standards (NBS) compiled published data and, based on statistical analysis, provided reference values of osmotic coefficients for various electrolyte solutions, using the average of multiple scientific datasets as the standard value for each electrolyte solution, along with the standard deviation. This reference data is expressed in the form of the Debye-Hückel equation, allowing users to calculate the corresponding osmotic coefficient by substituting the molality of the electrolyte solution into the equation. The osmotic coefficient can be used to calculate the water activity and freezing point of electrolyte solutions, thereby determining the standard values of these quantities for reference solutions, which can be used to calibrate measurement instruments for these properties. Sodium chloride is the most commonly used electrolyte. The reference values specified by relevant international and national standards are in good agreement with the results calculated using the reference data of the osmotic coefficient. Calculating the standard values of related physical and chemical quantities using the reference data of the osmotic coefficient allows for indirect traceability to SI units such as vapor pressure and electromotive force.