A Manganese Bioavailability Tool has been developed that simplifies the integrated Biotic Ligand Model but runs in MS Excel. It requires data input for site-specific dissolved organic carbon, pH and calcium. The tool uses a series of algorithms and constants which can be readily automated within current regulatory data management systems. The performance of this model against the original version is reviewed and discussed in this report. Guidance on the use of the Mn bioavailability assessment tool and interpretation of its outputs, along with screenshots, is given in this report. Equivalent tools have been developed for copper, zinc and nickel.