We report on an experimental procedure for assessing the modal density in a reverberation chamber (RC). The proposed method is based on the properties of time-reversal techniques as used for the coherent transmission of pulses through highly-reverberating media. A recent theoretical analysis has allowed linking the modal density to quantities that are easily accessible in practice, e.g., the field generated at given positions. These results are here applied to the problem of modal density assessment, showing that by sampling the electric field over a few points within the chamber it is possible to define an accurate modal-density estimator. The paper focuses on how the accuracy of the proposed estimator depends on the physical parameters of the RC, the number of field probes, the frequency of analysis, etc. By carefully choosing these parameters, the estimator is shown to be capable of attaining uncertainties of a score percent points; this, together with its being based on simple computations, make it a tool for real-time monitoring of different test configurations, allowing to check, e.g., how the loading of an RC affects its modal density.