This study was conducted on the prediction of adsorption capabilities of rice husks ash (RHA) for Copper (II) ions in wastewater solution by simulation study using the Fixed-bed Adsorption Simulation Tool (FAST) software in comparison with its experimental results. FAST simulated the efficiency of RHA as an adsorbent based on parameters of the contact time, Copper (II) ion concentrations, and RHA mass. Two calculation models were adopted using the software to determine the breakthrough curves of rice husks ash as an adsorbent, i.e., Homogeneous Surface Diffusion Model (HSDM) and Linear Diffusion Force (LDF) approximation model. The 2 h of contact time used while employing 10 to 80 ppm of metal concentration and RHA dosages of 5 to 10 g along with this simulation study. The findings have shown that a longer duration of contact time, the higher adsorption rate of copper (II) ions due to the increased possibility of RHA’s active sites for metal ions adsorption, corresponds to decreasing metal concentration in final metal ions solutions. The highest adsorption efficiency of 99.81 % was obtained whenever 10 ppm of copper (II) ion concentration was applied as initial metal ion concentration during the experiment. The adsorption rate was higher by increasing the adsorbent mass due to increased RHA active sites for metal ions adsorption at optimum pH 7.