Beta Dicalcium diphosphate is composed of eclipsed P2O7 groups linked through Ca2+ cations. The P-O(b) bonds involving the bridging O atoms are longer [average 1.620 (5) angstrom] than the others [average 1.517 (5) angstrom]. As the 'O4' tetrahedra are almost regular the displacement of the P atoms involves two sets of O-P-O angles: O-P-O congruent-to 112.7 (2) and O-P-O(b) congruent-to 106.0 (2)-degrees.