Interleaved boost converter is widely employed in automotive applications for Electric Vehicle (EV) and Hybrid Electric Vehicle (HEV). This paper presents two core loss calculation methods for inductors with ferrite core in interleaved boost converter. We verified usefulness of both core loss calculation methods. The one is experimental calculation method which is back calculated from temperature increase value of a core during driving. This method is possible to measure all core loss as heat. And, the other is theoretical calculation method which calculated from core loss - frequency characteristic graph on specification sheet of the core by applying Fourier series expansion method under square wave voltage magnetizing condition. This method is useful for calculating core loss when designing of inductor since core loss is possible to be predicted.