It is a critical design process to estimate the fractional errors of the Synthetic Aperture Radar (SAR) processor before implementation. The contribution of this paper is to identify the chief sources and types and to suggest an estimation technique for overall fractional errors of the space-based SAR processor using Range-Doppler Algorithm (RDA). Also, simulation is performed to the Experimental-SAR (E-SAR) processor to examine the practicability and efficiency of the technique, the results are discussed, and the solutions for problems are recommended. Therefore, this technique can be used to estimate the fractional errors of the space-based SAR processor using RDA.