Inventory Turnover in Days Formula is a business metric that reflects the efficiency of a company’s inventory management. It measures how quickly a company can purchase, sell and re-stock its inventories, with the goal of reducing total costs and maximizing profits. In other words, it’s an indicator of just how well the company manages its supply chain. The formula for inventory turnover in days is relatively simple: simply divide the cost of goods sold by the average inventory value for the period and multiply by 365. The result will give you an answer that reflects the number of times in a year that your inventory has been turned over.