Oceanic uptake of increasing atmospheric carbon dioxide emissions due to industrialization has raised environmental concerns that a more acidic ocean will have adverse effects on marine biota. This decrease in seawater pH, termed ocean acidification is expected to negatively impact marine organisms that use calcium carbonate to build their skeletons or shells. Past-ocean acidification events in the geologic record can be possible analogs for future ocean conditions. Therefore, a reliable tool is needed to reconstruct past seawater pH to understand potential responses on biology, the carbon cycle and global climate. Elemental Boron/Calcium ratios in calcium carbonate surface dwelling unicellular microorganisms; known as planktonic foraminifera have been suggested to reflect oceanic pH and ultimately has been used to estimate past atmospheric carbon dioxide concentrations. In addition to pH other chemical parameters such as carbonate ion, temperature and salinity have been proposed to influence the incorporation of boron into planktonic shells. The application of B/Ca to geologic studies requires that the various controls be resolved. In this study, the previously established boron isotope-pH proxy was used to compare with B/Ca ratios in multiple planktonic foraminifera species from modern ocean sediments. From this work an empirically defined relationship was developed for B/Ca to seawater pH. This calibration study will provide the ability for the paleoceanographic scientific community to reconstruct high resolution records of surface ocean pH beyond the instrumental record.