The modeling of single neurons has proved to be an indispensable tool in deciphering the mechanisms underlying neural dynamics and signal processing. In that sense, two types of single-neuron models are extensively used: the conductance-based models (CBMs) and the so-called 'phenomenological' models, which are often opposed in their objectives and their use. Indeed, the first type aims to describe the biophysical properties of the neuron cell membrane that underlie the evolution of its potential, while the second one describes the macroscopic behavior of the neuron without taking into account all its underlying physiological processes. Therefore, CBMs are often used to study 'low-level' functions of neural systems, while phenomenological models are limited to the description of 'high-level' functions. In this paper, we develop a numerical procedure to endow a dimensionless and simple phenomenological nonspiking model with the capability to describe the effect of conductance variations on non-spiking neuronal dynamics with high accuracy. The procedure allows to determine a relationship between the dimensionless parameters of the phenomenological 1 model and the maximal conductances of CBMs. In this way, the simple model combines the biological plausibility of CBMs with the high computational efficiency of phenomenological models, and thus may serve as a building block for studying both 'high-level' and 'low-level' functions of non-spiking neural networks.