CaMnO3 is a parent compound for various manganite systems exhibiting useful physical properties. Therefore, its structural and elastic properties are of general interest. In this paper, P–V equation of state of stoichiometric CaMnO3 is determined using energy dispersive X-ray diffraction. The measurements were carried out at a synchrotron beamline F2.1 (Hasylab, DESY) with samples compressed in a cubic-anvil diffraction press, MAX80, for pressures ranging up to 4.84 GPa. The experimental bulk modulus of CaMnO3, derived from the variation in the unit-cell volume with pressure by fitting the Birch–Murnaghan equation of state, is 154.4(3.3) GPa. The results are discussed on the basis of experimental and theoretical data for CaMnO3 and related compounds.