Accounting · Free tool
Days Inventory Outstanding Calculator
How many days of sales is sitting on the shelves? Inventory days, also called days inventory outstanding, turns an inventory balance into a time measure that is easy to compare across months and with peers. This calculator needs just two numbers and suits controllers, operations leads, and CFOs watching cash tied up in stock.
- OutputDays of inventory
- No sign-up
- Copy or print the result
- How it works ↓
Your entries stay in this browser. Use Fill example to see a finished page first.
What this accounting tool gives you
The result shows inventory days as the headline, with the inventory and cost of goods sold you entered beside it. In an operations review it gives a single figure to track month to month and to compare with receivables and payables days when you discuss the cash cycle.
What you enter
- Currency: USD by default, or EUR or GBP (only changes how amounts are formatted)
- Average inventory: the average stock balance over the year, zero or more
- Annual cost of goods sold: the cost of goods sold for the full year, above zero
Worked example
In the tool's example, average inventory is $50,000 and annual cost of goods sold is $365,000. Dividing $50,000 by $365,000 and multiplying by 365 gives 50 inventory days. In other words, the stock on hand would cover about 50 days of cost of goods sold at the year's average pace.
How are inventory days calculated?
Inventory days = average inventory ÷ annual cost of goods sold × 365. The result is rounded to two decimals.
The tool uses a 365-day year. Cost of goods sold is used rather than sales because inventory is carried at cost, which keeps both sides of the ratio on the same basis. If cost of goods sold is zero there is no divisor, and the tool shows a warning.
Tips before you use the result
- Use an average of opening and closing inventory, or monthly balances, rather than a single year-end figure that may be unusually high or low.
- Keep the period consistent: if you use a quarter's cost of goods sold, annualize it before entering it, since the formula assumes a full year.
- Compare inventory days with receivables days and payables days to see how long cash is tied up across the whole cycle.
- A falling number is usually good, but a sudden drop can also signal stockouts; check it against service levels.
Frequently asked questions
What is the formula for days inventory outstanding?
Days inventory outstanding equals average inventory divided by annual cost of goods sold, multiplied by 365. It tells you how many days the current stock would last at the average rate of use. With $50,000 of inventory and $365,000 of annual cost of goods sold, the result is 50 days.
Why use cost of goods sold instead of revenue?
Inventory is valued at cost, so dividing it by cost of goods sold compares like with like. Dividing by revenue would mix in your markup and make inventory look smaller than it is. This calculator asks for annual cost of goods sold for that reason.
What is a good number of inventory days?
It depends heavily on the industry. Perishable goods turn over in days, while some industrial parts sit for months. The useful comparison is your own trend over time and peers in the same sector. The calculator gives the figure; it does not rate it against a benchmark.
Are my inventory figures stored online?
They are not. Both inputs live in your browser's local storage, which keeps them on your own device, and the tool does not ask you to sign up. Reload the page later on the same device and the last figures you entered come back automatically.
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