Inventory Turnover Days Calculator (DIO)

Days inventory outstanding (DIO) converts your turnover ratio into plain calendar time: how many days a dollar sits on the shelf before it is sold. Divide 365 by the turnover ratio, where turnover equals annual cost of goods sold divided by average inventory. Worked example: COGS of $240,000 against an average inventory of $40,000 is a 6× turnover, so inventory days = 365 ÷ 6 ≈ 61 days. Cutting to 45 days frees about $10,000 of cash permanently tied up in stock.

1. 1

   Enter annual COGS

   Cost of goods sold over 12 months.

2. 2

   Enter average inventory

   (Beginning inventory + ending inventory) ÷ 2.

3. 3

   Read days on hand

   The calculator shows turnover ratio and days of stock.

• Using ending inventory only, which seasonal peaks distort

• Dividing by revenue instead of COGS — mixing margin into a volume metric

• Comparing your DIO to a different industry's benchmark