Days Inventory Outstanding – Accounting Superpowers

Days Inventory Outstanding

Days Inventory Outstanding

Days Inventory Outstanding is a financial ratio that indicates the average number of days it takes a company to sell its inventory.

Product based businesses work in cycles of inventory movement.

The cycle starts with buying inventory at cost from a supplier.  This inventory is then stocked in warehouses and retail shelves and eventually sold to a customer.  

The average number of days it takes a business to complete this cycle once is called Days Inventory Outstanding.

The Days Inventory Outstanding is also often referred to as Days Inventory or Days Sales of Inventory.  

What is the Formula of Days Inventory Outstanding? 

Days Inventory = (Average Inventory / COGS) x 365


Average Inventory= (Beginning inventory + Ending inventory)/2.  The Average Inventory is measured at cost and both the Beginning and Ending Inventory figures can be found in the Balance Sheet

The COGS figure can be found in the Income Statement

Example of Days Inventory Outstanding

Let's say that SUPERPOWER INC. has $5,000 worth of average inventory and $25,000 of COGS times in a one year period; the Days Inventory figure would be

DIO = ($5,000 / $25,000) x 365 = 73 Days.  

How is this it useful? 

Since the Revenue of a business has a direct correlation with the sale of inventory, any lag in the Days Inventory figure could mean that the revenue of the company will slow down.

The Days Inventory figure is especially useful when you compare it with another period. 

Ideally, businesses prefer the Days Inventory figure to keep falling since it means that inventory is selling faster.

An increase in the number of Days Inventory may be seen as a red flag by analysts and investors and needs to be further investigated by management.

Let's say the Days Inventory figure of 73 stated above goes to 93 over a two year period.  

Management needs to ask questions such as

Why has the number of days it takes to sell inventory increased?

Is it a macro level factor, such as a slow down in the economy? 


Does it have something to do with something inside the company?  

Based on their investigation, management may come up with a slew of issues such as - There could be a problem with logistics OR inventory sales at the retail store may have slowed down (For example, in a Fashion business, it could mean that the designs are getting obsolete.)

Once the root cause of the issue is identified, management can take steps to address it.  

For a full breakdown of other ratios that are useful in understanding the inner workings of a business, you can read our article on Ratio Analysis


The content provided on and accompanying courses is intended for educational and informational purposes only to help business owners understand general accounting issues. The content is not intended as advice for a specific accounting situation or as a substitute for professional advice from a licensed CPA. Accounting practices, tax laws, and regulations vary from jurisdiction to jurisdiction, so speak with a local accounting professional regarding your business. Reliance on any information provided on this site or courses is solely at your own risk.

Tax and accounting rules and information change regularly. Therefore, the information available via this website and courses should not be considered current, complete or exhaustive, nor should you rely on such information for a particular course of conduct for an accounting or tax scenario. While the concepts discussed herein are intended to help business owners understand general accounting concepts, always speak with a CPA regarding your particular financial situation. The answer to certain tax and accounting issues is often highly dependent on the fact situation presented and your overall financial status.