What Is Average Inventory?

Average inventory is a calculation that estimates the value or number of a particular good or set of goods during two or more specified time periods. Average inventory is the mean value of inventory within a certain time period, which may vary from the median value of the same data set, and is computed by averaging the starting and ending inventory values over a specified period.

Understanding Average Inventory

Inventory is the value of all the goods ready for sale or all of the raw materials to create those goods that are stored by a company. Successful inventory management is a key focal point for companies as it allows them to better manage their overall business in terms of sales, costs, and relationships with their suppliers.

Since two points do not always accurately represent changes in inventory over different time periods, average inventory is frequently calculated by using the number of points needed to more accurately reflect activities across a certain amount of time.

For instance, if a business was attempting to calculate the average inventory over the course of a fiscal year, it may be more accurate to use the inventory count from the end of each month, including the base month. The values associated with each point are added together and divided by the number of points, in this case, 13, to determine the average inventory.

The average inventory figures can be used as a point of comparison when looking at overall sales volume, allowing a business to track inventory losses that may have occurred due to theft or shrinkage, or due to damaged goods caused by mishandling. It also accounts for any perishable inventory that has expired.

The formula for average inventory can be expressed as follows:

Average Inventory = (Current Inventory + Previous Inventory) / Number of Periods

Average inventory is used often in ratio analysis; for instance, in calculating inventory turnover.

Moving Average Inventory

A company may choose to use a moving average inventory when it’s possible to maintain a perpetual inventory tracking system. This allows the business to adjust the values of the inventory items based on information from the last purchase.

Effectively, this helps compare inventory averages across multiple time periods by converting all pricing to the current market standard. This makes it similar to adjusting historical data based on the rate of inflation for more stable market items. It allows simpler comparisons on items that experience high levels of volatility.

Example of Average Inventory

A shoe company is interested in better managing its inventory. The current inventory in its warehouse is equal to $10,000. This is in line with the inventory for the three previous months, which were valued at $9,000, $8,500, and $12,000.

When calculating a three-month inventory average, the shoe company achieves the average by adding the current inventory of $10,000 to the previous three months of inventory, recorded as $9,000, $8,500 and $12,000, and dividing it by the number of data points, as follows:

Average Inventory = ($10,000 + $9,000 + $8,500 + $12,000) / 4

This results in an average inventory of $9,875 over the time period being examined.

What Is the Average Age of Inventory?

The average age of inventory is the average number of days it takes for a firm to sell off inventory. It is a metric that analysts use to determine the efficiency of sales. The average age of inventory is also referred to as days’ sales in inventory (DSI).

Formula and Calculation of Average Age of Inventory

The formula to calculate the average age of inventory is:


$\begin{aligned} &\text{Average Age of Inventory}= \frac{ C }{ G } \times 365 \\ &\textbf{where:} \\ &C = \text{The average cost of inventory at its present level} \\ &G = \text{The cost of goods sold (COGS)} \\ \end{aligned}$​Average Age of Inventory=GC​×365where:C=The average cost of inventory at its present levelG=The cost of goods sold (COGS)​

What the Average Age of Inventory Can Tell You

The average age of inventory tells the analyst how fast inventory is turning over at one company compared to another. The faster a company can sell inventory for a profit, the more profitable it is. However, a company could employ a strategy of maintaining higher levels of inventory for discounts or long-term planning efforts. While the metric can be used as a measure of efficiency, it should be confirmed with other measures of efficiency, such as gross profit margin, before making any conclusions.

The average age of inventory is a critical figure in industries with rapid sales and product cycles, such as the technology industry. A high average age of inventory can indicate that a firm is not properly managing its inventory or that it has an inventory that is difficult to sell.

The average age of inventory helps purchasing agents make buying decisions and managers make pricing decisions, such as discounting existing inventory to move products and increase cash flow. As a firm’s average age of inventory increases, its exposure to obsolescence risk also grows. Obsolescence risk is the risk that the value of inventory loses its value over time or in a soft market. If a firm is unable to move inventory, it can take an inventory write-off for some amount less than the stated value on a firm’s balance sheet.

Example of How to Use the Average Age of Inventory

An investor decides to compare two retail companies. Company A owns inventory valued at $100,000 and the COGS is $600,000. The average age of Company A’s inventory is calculated by dividing the average cost of inventory by the COGS and then multiplying the product by 365 days. The calculation is $100,000 divided by $600,000, multiplied by 365 days. The average age of inventory for Company A is 60.8 days. That means it takes the firm approximately two months to sell its inventory.

Conversely, Company B also owns inventory valued at $100,000, but the cost of inventory sold is $1 million, which reduces the average age of inventory to 36.5 days. On the surface, Company B is more efficient than Company A.