In this work, a nonlinear behavioral model is proposed for air-gapped ferrite-core inductors working up to magnetic saturation. The component is represented through the series connection of a nonlinear conservative inductor and a linear resistor, accounting for the instantaneous losses in both the windings and the core. The model is identified and validated through experimental measurements collected on a real buck converter. A very limited set of inductor voltages and currents is used for parameter identification. Some model coefficients depend explicitly on the air-gap length, which is useful for converter design purposes.