Susceptibility-induced field inhomogeneities in both space and time make B0-shimming a prerequisite for cardiac MRI at ultra-high field. All individual terms of the static 3rd-order spherical harmonics shim system were calibrated. Field mapping and calculation of shim currents are performed in customized B0DETOX software. Analysis of B0-inhomogeneities is later tested both in measurement of an ex-vivo pig heart and in-vivo in humans. The adjustment of the shim volume to the three measured slices in a healthy volunteer reduced the standard deviation of the field map by 4%, 19% and 18% compared to shimming of the global heart.