A self-focusing method applicable to digital lensless holographic microscopy is presented. The method searches for the global minimum of the area enclosing a given amount of energy in a region surrounding the object of interest. The proposed modified enclosed energy method has been tested on self-focusing experimental holograms of a paramecium specimen and a section of the head of a drosophila melanogaster fly. The presented self-focusing technique also has been contrasted with some of the already reported methods to seek the best focus image.