This article introduces alternative equations to undertakeStage-wise analysis stage-wise analysisAnalysis and numerically estimate the theoretical number of stages in extractionExtraction and strippingStripping circuits, initially focusing on copper solvent extractionCopper solvent extraction but with potential application to single or binary metalMetal systems. These equations allow for faster, more direct calculation of efficiencyEfficiency, inter-stage concentrations, and stage count. The presented extractionExtraction and strippingStripping ratio modelsModel have been developed by incorporating factors initially discarded when the Kremser equation was formulated. Hence, the constant ratio theory is followed and governs the fundamental countercurrent solvent extractionSolvent extraction operationOperation. Comparing the extractionExtraction–strippingStripping modelsModel with a preliminary experimental validationExperimental validation, which consisted of running continuous countercurrent copper solvent extractionCopper solvent extraction experiments in a mini-scale mixer-settler unit plant, it has been demonstrated that theExtraction–stripping yields extractionExtraction yield and strippingStripping yield can be predicted with an accuracy of 80% to 100%. In addition, the projectedStage-wise analysis stage-wise analysisAnalysis for the strippingStripping section also deviated by no more than 5% compared to the continuous Cu-solvent extractionSolvent extraction experimental results. However, the extractionExtraction stage-wise analysisAnalysis needs to be re-formulated to increase the prediction, which was around 50%.