A method for determining detergent concentration includes performing a photometric analysis of a wash fluid during an article laundering process, and determining a concentration of a detergent within the wash fluid based at least in part upon the photometric analysis. Furthermore, an apparatus for determining detergent concentration includes a fluid chamber to hold a wash fluid for washing articles, and an optical sensor optically coupled to the fluid chamber to determine a detergent concentration within the wash fluid based at least in part upon photometric properties of the wash fluid.