We develop a simple and approximate model for hysteresis and eddy currents in cylindrical magnetic cores. The model characterizes the core by the magnetic properties of its material (mu,psi0, and sigma) and its geometry (perimeter and area of cross section and core length). The model is compatible with common electrical simulators, such as spice, and allows a fast and approximate computation of both hysteresis and eddy-current power losses, impedance, flux, and field. We extended the model to parallelepipedal geometries, and we checked it by comparison to previous models and by experimentation