This paper reports a mathematical model for the calculation of various losses in a dual electrolyte membraneless electrolytic cell (DEME) for CO2 to formic acid conversion. The microfluidic characteristics of the cell were explored. Based on the electrochemical equilibrium states, major limiting factors, including mass transfer constraints, kinetic losses, and overpotentials, were considered. In particular, the acid-base interface and the neutralization losses therein were identified. We also quantified the electrical resistance losses on electrodes and within the micro-channels. Computational results were validated against previous experimental data. To our best knowledge, this is the first model studying the dual electrolyte arrangement and the associated losses, which can be used to develop future parametric optimization strategies.