ABSTRACT Agricultural waste biomass as a precursor for the synthesis of activated carbons has increased in recent years. In spite of transportation cost, agricultural waste biomass is one of an environmentally friendly, readily available and known as renewable sources compared to conventional activated carbon which is very expensive and exhaustible. That is the main reason activated carbon derived from agricultural waste biomass has been widely used in a variety of applications in the environment and industry for the separation, retrieval, modification, and removal of diverse substances in the liquid and gas phases. The purpose of this research is to produce activated carbon (AC) from corncob through carbonization followed by chemical activation with sodium hydroxide. Initially, the corncob was ground and sieved into a powder form with a mesh size of 500 µm. Later, the powder was chemically activated with sodium hydroxide at different impregnation ratios (1:1, 1:2, and 1:4) under activation temperatures of 200 oC. The percentage of carbon yield and ash content were evaluated using a mathematical approach. The results revealed that the sample impregnated at ratio of NCAC 1:4 showed the lowest ash content (6.58 %) with highest carbon yield of 20.52 %. As the impregnation ratios of sodium hydroxide increases, these entrapped chemicals in the activated corncob contributed in high carbon yield and reduced ash content.