Several methods are available for calculating shear viscosities of liquids from molecular dynamics simulations. There are equilibrium methods based on pressure or momentum fluctuations and several nonequilibrium methods. For the nonequilibrium method using a periodic shear flow, all relevant quantities, including the accuracy, can be estimated before performing the simulation. We compared the applicability, accuracy and efficiency of this method with two equilibrium methods and another nonequilibrium method, using simulations of a Lennard-Jones fluid and the SPC and SPC/E [(extended) simple point charge] water models.