Nowadays, the consumption of non-renewable energy is high. As a result, the availability of this energy is decreasing. Because of this, other energy alternatives are needed. One example of another option is the use of biomass. An example of using biomass is the gasification process. This process was carried out in a device called a gasification stove, namely a gasifier. A gasifier has been developed to produce an optimal combustion system. The constraints in this development are costs for manufacture and the potential for failure. Therefore, simulations using Ansys Computational Fluid Dynamics (CFD) software student versions were carried out to reduce the costs for manufacture and the potential for failure of the gasifier. The simulation contains dimensional variations and the number of air inlets of gasifier of downdraft gasifier, updraft gasifier, and entrained flow gasifier. Further, the influence of the dimensions and quantity of inlet that affect each design’s efficiency and the temperature was examined. The simulation results show that the best dimensions for the downdraft gasifier, updraft gasifier, and entrained flow gasifier are height and diameter of 50cm; 14.5cm (A1), 144cm; 70cm (C1), and 900cm; 300cm (B3), respectively. The best number of air inlets of A1, C1, and B3 gasifiers is 6, 1, and 6, respectively. Thus, the efficiency of each gasifier A1, C1, and B3 are 11.393%, 9.354%, and 50.885%, respectively. Furthermore, the A1, C1, and B3 gasifiers temperatures were 1055.25 K, 1383.44 K, and 3580.15 K, respectively. Therefore, this study suggested that the gasifier development could be optimized using simulation to reduce manufacturing costs and failures.