The physical properties of sodium borosilicate glasses were calculated directly from their chemical compositions in the whole glass-forming region. These properties included molar volume, refractive index, thermal expansion coefficient, elastic moduli, and glass transition temperature. The physical property values corresponding to the structural unit were estimated and then the calculation was carried out by accumulating the physical property values depending on the chemical composition of the glass. In the case of sodium borosilicate glass, the structural units are BO3/2, BO4/2Na,BO2/2ONa,BO1/2O2Na2,SiO4/2,SiO3/2ONa,SiO2/2O2Na2, and SiO1/2O3Na3. To conduct the calculation, the structural units’ physical property values were estimated by analyzing experimental data extracted from the database of glass properties, INTERGLAD. The calculated values were similar to the experimental data in the whole glass-forming region. Furthermore, the calculation method provided, quantitatively, the structural units’ contributions to the glass’ physical properties. This study demonstrates that using the concept of structural units to calculate the physical properties of sodium borosilicate glass is a simple and powerful predictive tool.