Inventory Turnover

What Is Inventory Turnover?

Inventory turnover is a great indicator of how efficiently your company turns inventory into sales. This ratio indicates how many times the inventory is sold during a certain period of time — over a year, for example. Knowing how to calculate inventory turnover rate will help you to plan future inventory purchases and optimize your stock.

Days In Inventory* (DII) helps you to understand inventory turnover even better because it puts the ratio into a daily context. The DII value shows the average number of days it takes you to sell the current inventory on hand. Generally, a higher inventory turnover (but lower inventory turnover period) is preferred, but it varies from one industry to another.

These numbers are important because they influence a significant source of your profit, the margin. A decrease in inventory turnover means that stock is moving slower and you’re selling fewer goods are being sold or you’ve had to lower the markup rate for some reason. This will lower your margin. Investors are interested in knowing how liquid your company’s inventory is and how fast you can turn it into cash. If it can’t be sold, it’s worthless to your company and to potential business partners.

*Also known as days sale of inventory (DSI), days inventory outstanding (DIO), days inventory, inventory period, inventory turnover period, or simply average days to sell the inventory.

How to Calculate Inventory Turnover?

The turnover ratio can be calculated by dividing sales or the cost of goods sold (COGS) with the average inventory. You can find Sales and COGS values on the income statement. The Company’s balance sheet reports the inventory on hand. The average inventory can be found by dividing the sum of the starting and ending inventory values.

Using COGS to find your inventory turnover is more accurate and realistic as it doesn’t include the markup. On the other hand, using sales is very common and might be necessary for comparative analysis.

Example of How to Calculate Inventory Turnover

Inventory at the beginning of the year: $100 000
Inventory by the end of the year: $120 000
Sales: $1 000 000
COGS: $600 000

Average inventory = (100 000 + 120 000) / 2 = $110 000

Based on sales:

Inventory turnover = sales / average inventory
1 000 000 / 110 000 = 9,09

Days in inventory = time period / inventory turnover = time period x (average inventory / sales)
365 / 9,09 = 365 x (110 000 / 1 000 000) = 40,15 days

Based on COGS:

Inventory turnover = COGS / average inventory
600 000 / 110 000 = 5,45

Days in inventory = time period / inventory turnover = time period x (average inventory / COGS)
365 / 2,27 = 365 x (110 000 / 600 000) = 66,97 days

High Inventory Turnover

The good

  • stronger sales and higher profitability
  • lower storage risks and fewer expenses
  • reduced need for financial resources for the acquisition of goods
  • increase the solvency
  • purchasing is tightly managed
  • lower risk of becoming stuck with obsolete stock

The bad

  • may indicate inadequate inventory levels
  • risk of running out of stock and losing sales to competitors
  • can refer to low cash reserves to maintain normal stock levels
  • may be due to large discounts that produce no or small profit

Low Inventory Turnover

The good

  • low inventory turnover is acceptable in situations where higher stock levels occur in anticipation of upcoming sales, rising prices or expected market shortages

The bad

  • weaker sales
  • excess inventory
  • which could suggest poor inventory management or low sales
  • it ties up company’s cash and makes it vulnerable
  • risk of inventory aging
  • flaws in the purchasing system
  • higher storage charges
  • obsolescence or deficiencies in the goods
  • can indicate overall marketing problems


  • Compare your inventory turnover or days in inventory values against the industry average.
  • Match current turnover rate to previous and planned ratios.
  • Only compare inventory turnover that uses the same approach (sales or COGS based).
  • Higher turnover is useless unless you make a profit on each sale.
  • Make sure you have enough stock with higher inventory turnover, so you won’t lose sales. This might cause an increase in expenses and lower your company’s profitability.
  • Inventory purchases made in preparation for special sale events can suddenly and sometimes artificially change the inventory turnover rate.
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