Inventory Days Outstanding (IDO) is a business metric used to measure the average amount of time it takes a company to sell its inventory. In other words, IDO is a measure of how efficient a company’s supply chain and internal operations are – the fewer days outstanding, the more efficiently the company works. IDO is calculated by dividing the total value of inventory at the end of the period by the total cost of goods sold during that period, then multiplying the result by 365. This figure can be further divided by the number of days in the period for an even more precise measurement. IDO is an essential metric for businesses to track in order to remain competitive and ensure their inventory management strategies are optimized.