The authors deal with the problem of estimating Radar Cross Section (RCS) for objects detected by high-resolution Frequency Modulated Continuous Wave (FMCW) radar. The difficulties of the problem are total loss detection in radar equation and discrete noise mitigation. The total loss consists of internal attenuation factors of the radar set on the transmitting and receiving paths, fluctuation losses during the reflection and atmospheric losses during propagation of the electromagnetic waves to and from the target. In order to detect the total loss, the authors utilize the method of adjusting the received power for a type of target that has already known the value of RCS. For discrete noise mitigation, we study an algorithm to detect outliers and filter noise in the received power signal. Data collected from three different types of commercial drones using a high-resolution FMCW radar system were preprocessed and used to calculate RCS values in the X-band frequency. The results indicate that the proposed method yields RCS values that are approximately consistent with the values published by other methods.