<p>This study focuses on the validation and optimization of an alternative method for measuring the moisture content of solid soap using the Kern analyzer, in comparison to the reference method (oven method). The samples taken directly from the production line are stored in a manner to keep their humidity constant, then parts in a whole are selected and cut into small pieces to finally have a set of granules from the different sampling points. The humidity level measurements are carried out using both the reference method and an alternative one, with a well-determined repetition. The statistical analysis of the measurement results corresponding to the linearity criterion revealed a perfectly linear equation of the regression line: <i>y</i> = 0.1785 ∗ <i>x</i> − 0.0053. The trueness tests enabled the establishment of a confidence interval (CI) for the average recovery at 98.77–102.08, which encompasses the 100%. The coefficient of variation of the intermediate fidelity, CVIF, was 0.61, and the coefficient of variation, CV, was 0.32%, both of which align very well with pharmaceutical standards. This novel validation approach, based on the use of the exactness profile, offers stronger guarantees in terms of reliability and adequacy of the decision. Furthermore, the optimization study carried out enabled the provision of sufficient guarantees, ensuring that all future outcomes generated by the method during its regular use will be sufficiently close to the actual value.</p>