The DC-DC converters using integrated magnetic components that may achieve high power density have gained attention in eco-friendly cars such as HEV and PHEV. Interleaved converters with close-coupled inductors and loose-coupled inductors are well known as the converters capable to achieve high efficiency with low volume and weight. As a new approach, an interleaved converter with integrated winding coupled inductors is proposed. This paper presents allowable power calculated method of these circuit topologies in order to realize further high power density. Following the design guidelines of allowable power calculated method for each coupled inductor, the downsizing effects of the magnetic components are compared to conventional interleaved boost converter in the same conditions from the allowable power viewpoints. As a result, CCM operation is effective for downsizing of the magnetic components in case of interleaved boost converter using loose-coupled and integrated winding coupled inductors. On the other hand, interleaved boost converter using close-coupled inductors is effective for downsizing of the magnetic components with CRM operation. This comparative data is discussed from theoretical and experimental viewpoints.