Three natural olivines with Fo 80 Fa 20 , Fo 71 Fa 29 , and Fo 62 Fa 38 compositions were investigated in situ at high pressure by single-crystal X-ray diffraction using a diamond-anvil cell up to c8 GPa at room temperature. The bulk modulus, K T0 , and its first pressure derivative, Ke, do not show any significant variation among the compositions investigated and, using the data on a further sample with Fo 92 Fa 8 composition recently investigated in the same laboratory and using the same experimental technique, we obtain, for the first time, a single equation of state for the entire Fo 92 Fa 8 -Fo 62 Fa 38 compositional range. The equation has the following coefficients: K T0 = 124.7(9) GPa and Ke = 5.3(3) and can be used for thermodynamic calculations involving the most common mantle olivine compositions.