Sea clutter is a major degrading factor in detection and tracking of targets very close to sea surface. Radar returns from the sea surface are a complex function of radar and sea surface parameters. Computer simulation of radar clutter can provide radar returns for cases where closed form expressions are not available, and experimental results are scarce and expensive. In this paper, a previously developed radar simulation program is extended to obtain sea clutter values for UHF L, S, C and X bands. The simulation program traces the backscattered electromagnetic waves in time in the radar background. The returns are individually recorded along with their polarization, amplitude, phase, arrival time and Doppler shift. The program is modular so desired radar and sea surface models can be inserted to realize various radar scenarios. The returns can be individually processed and the characteristics of clutter can be investigated in time and frequency even for scenarios which are difficult to be realized experimentally. The simulation results for the sea surface backscatter normalized radar cross section (NRCS) are presented with respect to the variations in polarization, sea state, grazing angle and frequency. When the simulated NRCS values are compared with the available data in the literature, a very good agreement is observed. The radar simulation program proves itself to be a versatile tool to generate radar scenarios on the computer and obtain reliable synthetic data for clutter which can be used for more successful signal processing algorithms for target detection and clutter suppression.