Elachista planca is a moth of the Elachistidae family that is endemic to Kenya. The wingspan is about 9.6 mm. The ground colour of the forewings is brownish grey, indistinctly delimited whitish transverse fascia. There is a white spot on the costa and another similar spot slightly before it at the tornus. The fringe scales in the apex are white, but otherwise grey. The hindwings, including the fringe, are pale brownish grey.