The Weighted Average Inventory Costing Method is an accounting system used to value inventory. It assigns a relevant cost to each item based on the average cost of all items in stock. This method run periodically as more purchases are made, allowing for an updated cost calculation based on the actual purchasing price of recent acquisitions. By using this costing method, companies can accurately account for the cost of goods sold and inventory on hand. In addition, it helps in determining pricing strategies and making better purchasing decisions.