Isobaric heat capacities (CP) of Mg2SiO4 forsterite and ringwoodite were measured by differential scanning calorimetry in the temperature range of 306–833 K. The measured CP of Mg2SiO4 forsterite was consistent with those reported by previous studies. On the other hand, the present CP of Mg2SiO4 ringwoodite was about 3–5% larger than those measured by previous researchers. The calorimetric data of Mg2SiO4 ringwoodite were extrapolated to 2500 K using a lattice vibrational model calculation, which well reproduced the low-temperature CP data measured by thermal relaxation method. The calculated CP shows good agreement with the present calorimetric data. The obtained CP was expressed by the polynomial of temperature: CP = 164.30 + 1.0216 × 10−2T + 7.6665 × 103T−1 – 1.1595 × 107T−2 + 1.3807 × 109T−3 [J/(mol·K)] in the range of 250–2500 K.