Phosphorus magnetic resonance spectroscopy (31P-MRS) delivers unique information to aid our understanding of cardiac metabolism. To quantify “absolute” concentrations of phosphorus metabolites (i.e. in recognised units such as mmol / kg wet weight), sensitivity calibration and transmit field correction are required. Ultrahigh field (>7 T) magnets and the use of multichannel RF coils make this even more challenging. In this study, we investigate the feasibility of absolute concentration of phosphorus metabolites in the human heart at 7T, compare our findings to literature values and evaluate reproducibility with different coils and different MR systems.