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Inventory period calculator

Days Inventory Outstanding — how long stock sits before it sells: average inventory ÷ cost of goods sold × days, or simply days ÷ inventory turnover if you already know the ratio. Lower is faster turnover and better cash flow.

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The Inventory period calculator turns Method, Annual COGS, Average inventory, Inventory turnover (×), Days in period into Inventory period (days), Inventory turnover (×), instantly and for free. For instance, with Method = From COGS & inventory, Annual COGS = $500,000.00, Average inventory = $75,000.00, Inventory turnover (×) = 8.5 and Days in period = 365 it returns Inventory period (days) = 54.75 and Inventory turnover (×) = 6.667.

How to use it

  1. Enter your values: Method, Annual COGS, Average inventory, Inventory turnover (×), Days in period.
  2. Read the result instantly: Inventory period (days), Inventory turnover (×).

Frequently asked questions

What does the Inventory period calculator actually compute?

It takes Method, Annual COGS, Average inventory, Inventory turnover (×) and Days in period and derives Inventory period (days) and Inventory turnover (×) from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

5 values: Method, Annual COGS ($), Average inventory ($), Inventory turnover (×) and Days in period. Nothing else is required — no account, no file upload.

Can you show a worked example?

With Method = From COGS & inventory, Annual COGS = $500,000.00, Average inventory = $75,000.00, Inventory turnover (×) = 8.5 and Days in period = 365, the calculator returns Inventory period (days) = 54.75 and Inventory turnover (×) = 6.667. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Method = From turnover ratio, Annual COGS = $1,000,000.00, Average inventory = $150,000.00, Inventory turnover (×) = 17 and Days in period = 730 instead, Inventory period (days) goes from 54.75 to 42.941 — which is why it is worth testing a few scenarios rather than trusting a single figure.

Which “Method” option should I choose?

You can pick between « From COGS & inventory » and « From turnover ratio ». Each one changes what the calculator works out, so switch and compare — the default is « From COGS & inventory ».

What does it give for smaller values?

Scaled down to Method = From COGS & inventory, Annual COGS = $250,000.00, Average inventory = $37,500.00, Inventory turnover (×) = 4.3 and Days in period = 183, Inventory period (days) comes out at 27.45. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Running the week: issuing an invoice or a quote, knowing what is in stock and what to reorder, and seeing whether cash covers what is due.

What is the most common mistake?

Reading profit as cash. A profitable month with sixty-day payment terms can still leave the account empty — the two numbers answer different questions.

What is the difference between the Inventory period calculator and the Average collection period calculator?

This one returns Inventory period (days) and Inventory turnover (×); the Average collection period calculator returns Average collection period (days) and Receivables turnover (×). That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Payback period calculator is the closest one after this: Work out how long an investment takes to pay for itself.

Further reading

All guides →
ExplainerThe Cash Conversion Cycle: the Number That Explains Why You Are Out of CashCCC = DIO + DSO − DPO. It is the number of days your cash is out of your hands, and it is the reason a profitable, growing business runs out of money. Worked end to end, with the negative-cycle case that makes suppliers your cheapest lender.ExplainerGMROI: the Inventory Number That Outranks MarginGross margin return on inventory investment divides gross margin by the cash tied up in stock. It exists because margin alone ranks products wrongly: a 60% margin turning twice a year loses to a 25% margin turning twelve times.ExplainerCost of Goods Sold Is What Left the Shelf, Not What You BoughtOpening stock 40,000, purchases 120,000, closing stock 35,000 — the cost of goods sold is 125,000, and it is larger than the purchases because the shelf gave up 5,000 of what was already there.ExplainerThe Count Says 48,200 and the Books Say 50,000A gap of 1,800 is a shrinkage rate of 3.6 %. The percentage is the number that travels; the absolute figure is the one that pays for the fix.ExplainerA 30 % Sell-Through Is Excellent or Alarming, and the Missing Word Is "When"120 units sold out of 400 received is 30 %. Whether that is a success depends entirely on how long it took, and the rate on its own does not carry the answer.ExplainerFour Points of Service Level Cost 41 % More StockGoing from a 95 % service level to 99 % raises the z-score from 1.645 to 2.326 and the safety stock from 346 units to 488. The last few points of availability are the expensive ones.