Demand forecasts form the basis of all supply chain planning. This research is focused on the simulation of cement manufacturing process to find out the production loss of machines that will affect the production quantity, and analyzing different methods of forecasting to compare their errors so that appropriate forecasting method is identified to predict correct demand. Depending on the forecasting, the simulation process applied can aid to estimate amount of raw materials require producing particular amount of cement to fulfil the demand including the losses in various steps of manufacturing process. Moreover, seasonality of demand is considered where the same demand will repeat at a particular period. The longer horizon forecasts, using Holt-Winters method, are usually less precise than the shorter horizon forecast; that is, long horizon forecasts have larger standard deviations. This investigation on overall demand could facilitate the comparison between the futures forecasted demand and the overall customer demand.