A document size identification module receives a single scan of a document and detects for at least one of a black to white transition and a white to black transition. The black to white transition may represent a transition from an overscan area of a platen to a document. The white to black transition may represent a transition from the document to the overscan area of the platen. By detecting at least one of the black to white transition and the white to black transition, the document width may be determined. By determining the document width, the document size may be identified.