The dynamic viscosity of water, glycerol, and its mixtures over a wide range of temperatures, including the supercooled region, was calculated resorting to several predictive approaches and compared to published data. The temperature dependence of the viscosity of the pure components can be described within the experimental error using different empirical equations. However, the best fit is obtained by the Avramov-Milchev equation, taking into account that this equation has only two adjustable parameters. The same model was also used to describe the viscosity of the mixtures over the entire range of temperatures and compositions where experimental data are available and to extrapolate the viscosities of the mixtures at temperatures close to the glass transition. We calculated the viscosities of glycerol-water mixtures, over the entire range of compositions, between (238.15 and 273.15) K. The agreement with experimental data in the stable liquid region is very good, which makes our predictions in the supercooled region fairly reliable. The analysis of the glycerol-water mixtures reveals that, in contrast to that previously found in other aqueous polyol solutions such as sucrose and trehalose, the temperature and composition dependence of the viscosity cannot be described with a scaled Arrhenius equation. At low temperatures, the excess viscosity of the glycerol-water mixtures can be very well described by a regular-like solution coefficient.