[en] The magnetic fields of stellarators and, in general, all not strictly axisymmetric toroidal fusion devices exhibit magnetic islands. They strongly influence the confinement properties and are exploited in divertor concepts. So, the existence and the structure of the magnetic islands are an important issue in configuration design. Codes that determine finite-plasma-beta stellarator equilibria while fully accounting for their island structures exist, e.g. the Princeton Iterative Equilibrium Solver. An alternative approach to the assessment of magnetic islands in finite-beta stellarator equilibria has been developed with the method of perturbed equilibria. Since a perturbed equilibrium represents a small deviation from an equilibrium, ideal magnetohydrodynamic (MHD) stability theory and ideal MHD stability codes, e.g., the Code for the Analysis of 3-dimensional Equilibria, can be used to determine a perturbed equilibrium. A widespread tool for the calculation of finite-beta stellarator configurations is the Variational Moments Equilibrium Code which is based on the assumption of nested surfaces. With the ideal MHD picture and this assumption surface currents on the surfaces with rational rotational transform are used to model islands. The width of an island can be estimated from the strength of such a surface current which in turn depends on the discontinuity of the ideal MHD normal displacement computed by the CAS3D code. The PIES code and this alternative method have been applied to the National Compact Stellarator Experiment and the Wendelstein 7-X stellarator and yield comparable island sizes. (author)