A cartridge for the inked ribbon of a calculating or other office machine, of the type comprising a platen, a plurality of printing styli disposed in front of the platen at a short distance therefrom, a motive shaft, two fixed stops for transverse positioning of the cartridge with respect to the platen and a longitudinal positioning block. The cartridge comprises a container of substantially parallelepipedal form having a larger side provided with a recess defining two lateral arms. An inked ribbon closed in a loop is disposed inside the container and extends therein between an inking roller and a ribbon tensioning element. The ribbon has a substantially rectilinear portion which emerges from the said lateral arms and spans the recess, parallel to the larger side. The inking roller is housed in a first of the lateral arms, is engageable by the motive shaft of the machine driving the ribbon, and has its diameter substantially equal to a smaller side of the container, while the ribbon tensioning element is housed in the second of the said lateral arms. Two abutment surfaces and a recess co-operate with the said fixed stops and the positioning block, respectively, when the cartridge is mounted on the machine in order to position the ribbon exactly with respect to the platen and the printing styli.