MODERN MARINE SHIPS OFTEN INTRODUCE RADAR CROSS SECTION (RCS) SPECIFICATION OF VEHICLES IN ADDITION TO OTHER MORE CONVENTIONAL REQUIREMENTS SUCH AS SPEED, WEIGHT, AND PAYLOAD. IN CALCULATING THE RCS OF COMPLEX TARGETS SUCH AS MARINE SHIPS THERE ISN'T ANY EXACT CALCULATION METHOD, SO THE RCS ESTIMATION OF THESE TARGETS IS A GREAT CHALLENGE. ACADEMIC STUDIES PURPOSES HAVE ENCOURAGED THE SPECIALISTS AND RESEARCHERS TO STUDY AND EXTEND THE NEW FIELDS OF THIS SUBJECT; SUCH AS NEW ALGORITHMS, OPTIMUM DESIGN OF CODES AND SO ON.IN THIS PAPER A PROCEDURE FOR CALCULATING THE RADAR CROSS SECTION OF MARINE SHIPS IS PRESENTED WHICH IS BASED ON GRIDING THE OUTER SURFACE AND PROCESSING THE 3 DIMENSIONAL (3D) REAL MODEL OF THE VEHICLE. THEN A PROCESS IS PRESENTED TO CALIBRATE THE ACQUIRED NUMERICAL RESULTS. WITH DOING IT: L) THE BIASING ERROR OF THE CALCULATIONS WILL BE REMOVED AND 2) THE RESULTS WILL BE MEANINGFUL AND INTERPRETABLE FOR FUTURE ACTIVITIES (I.E. RCSR). ACCORDING TO THIS METHOD, THE RESULTS OF A CERTAIN FAST SHIP ARE PRESENTED. FIRST, THE 3D SURFACE OF THE COMPLEX TARGET IS DIVIDED TO N DISCRETE SIMPLE SCATTERERS AND THE TOTAL FAR-FIELD RCS OF THE TARGET IS CALCULATED WITH THE SUPERPOSITION OF ALL OF THESE SCATTERERS IN A COHERENT SUMMATION. THE MAIN SPECIFICATION IN CALCULATING THE RCS WITH THIS METHOD IS THAT IN ADDITION TO THE MAGNITUDE, THE EFFECT OF THE PHASE OF EACH SCATTERER IS CONSIDERED AND WITH DOING CALIBRATION PROCESS, SCALED NUMERICAL VALUES WITHOUT BIASING ERROR WILL BE ACQUIRED.