Purpose This paper discusses the inventory planning of a supply chain, which consists of a manufacturer, distributor and retailer. Design/methodology/approach The differential evolution algorithm is developed to minimize the total system-wide cost, which consists of supply chain inventory capital, supply chain ordering/set-up cost and supply chain stock-out cost. Findings The differential evolution algorithm helps in determining ordering/production quantity and inventory/service level that should be maintained by each member of the supply chain. Originality/value The algorithm developed is useful in increasing the customer service level and in decreasing the inventory level throughout the supply chain. © 2005, Emerald Group Publishing Limited