A demand forecasting system for calculating recommended supply comprises: a database unit storing a standard calculation period for each item, a standard visit period, a standard supply period, a first supply date, first supply, which is quantity of goods supplied at the first supply date, a second supply date, and second supply, which is quantity of goods supplied at the second supply date; an average sales calculation unit calculating average daily sales for each item from the standard calculation period for each item, the first supply, and the second supply; an estimated inventory calculation unit calculating previous estimated inventory from the average daily sales; a recommended supply calculation unit calculating recommended supply for each item from the previous estimated inventory, the average daily sales, and the standard supply period; and a display unit displaying the average daily sales, the recommended supply, the standard calculation period, the standard visit period, and the standard supply period.
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