<p>This study introduces a novel mathematical framework for returns on savings in nanofinance (NF). NF is an informal, unregulated financial mechanism established by impoverished populations lacking access to conventional microfinance services. We present a hierarchical stochastic differential equation (SDE) model, grounded in a drift-diffusion processes, to elucidate the multi-tiered structure of NF systems. To validate the proposed SDE framework, the parameters of the SDE model were calibrated through orthogonal and non-orthogonal minimizations of the Kullback-Leibler divergence against empirical returns. Computational analyses show that the calibrated SDE model approximates observed return dynamics in NF, thereby providing a quantitative foundation to inform the formulation of economic policies aimed at enhancing financial inclusion for extremely poor populations across developed and developing economies. The contribution of our work lies in its rigorous characterization of previously unmodeled hierarchical mechanisms underlying profit generation in NF. By synthesizing exogenous and endogenous factors driving return dynamics—from macroeconomic fluctuations to intra-group behavioral interactions—our model advances the economic understanding of NF sustainability. This structural insight is critical for ensuring the sustained operation of NF systems, which serve as vital platforms for poverty alleviation initiatives and inclusive financial intermediation among globally vulnerable demographics.</p>