Days Inventory Outstanding (DIO) Calculator
Calculate days inventory outstanding and inventory turnover to assess inventory efficiency and cash tied up in stock.
Enter beginning inventory, ending inventory, cost of goods sold, and the period length to measure average time inventory remains on hand.
Days Inventory Outstanding (DIO) Calculator
Calculate days inventory outstanding and inventory turnover to assess inventory efficiency and cash tied up in stock.
About Days Inventory Outstanding
Days inventory outstanding (DIO) estimates how long inventory sits before it is sold or consumed. It is a core working-capital metric alongside days sales outstanding and days payable outstanding. Supply-chain managers, controllers, and credit analysts use DIO to see how much cash is tied up in stock and whether inventory is turning faster or slower than last period or than peers.
The calculator first averages beginning and ending inventory, then computes inventory turnover as COGS ÷ average inventory and DIO as average inventory ÷ COGS × days in the period. Using average inventory reduces the distortion of a single snapshot. With beginning inventory $12,000, ending inventory $8,000, COGS $50,000, and a 365-day year, average inventory is $10,000, turnover is 5.00, and DIO is 73.00 days. A 360-day convention is sometimes used in banking models and will produce a slightly different day count from the same balances.
Use DIO when diagnosing a cash conversion cycle, comparing two product lines, or checking whether a buildup is seasonal or structural. Lower DIO can free cash, but a very low figure can also mean stockouts if lead times are long. Always match COGS and inventory to the same period and costing method. Mixing a quarterly COGS figure with a 365-day assumption will understate days on hand.
DIO does not capture write-downs, consignment stock, or in-transit goods unless those amounts are in the inventory and COGS figures you enter. FIFO versus weighted-average costing can move both the average and the ratio. Compare DIO with service-level data, not in isolation, and document whether the period is a year, quarter, or custom count of days.
DIO is one leg of the cash conversion cycle: CCC = DIO + DSO − DPO. Improving DIO without hurting fill rates usually means better forecasting, fewer obsolete SKUs, or tighter receiving. If beginning and ending inventory differ sharply because of a one-time build, consider a 12-month average inventory instead of the two-point average used here. Always pull COGS from the income statement that covers the same days you enter, and exclude consignment inventory you do not own.
Days Inventory Outstanding Examples
These worked examples follow the same formula as the calculator and provide a practical way to check your inputs.
| Input | Output | Notes |
|---|---|---|
| Beginning inventory $12,000; ending $8,000; COGS $50,000; 365 days | 73.00 days (turnover 5.00) | Average inventory of $10,000 is held for 73 days at this cost of sales run-rate. |
| Beginning inventory $6,000; ending $4,000; COGS $25,000; 360 days | 72.00 days (turnover 5.00) | The same five turns on a 360-day year produce 72 days outstanding, a common bank-model convention. |
| Beginning inventory $80,000; ending $120,000; COGS $400,000; 365 days | 91.25 days (turnover 4.00) | A rising inventory balance pulls average stock to $100,000 and lengthens DIO to about a quarter of a year. |
How to Calculate Days Inventory Outstanding
- Take beginning inventory, ending inventory, and cost of goods sold from the same accounting period.
- Enter the period length in days (365 for a year, 90 or 91 for a quarter, or the exact day count).
- Select Calculate to see average inventory, inventory turnover, and days inventory outstanding.
- Compare DIO with last period, peer medians, and service-level targets before cutting stock.
Days Inventory Outstanding FAQ
What does DIO measure?
DIO estimates the average number of days inventory is held before it is sold or used. It converts inventory turnover into a days-on-hand figure that is easier to compare with lead times.
Is lower DIO always better?
Lower DIO can indicate faster movement and less cash tied up in stock, but a very low level can also cause stockouts. Compare it with demand, lead times, and peer ranges.
Why use average inventory?
Average inventory reduces distortion from a single opening or closing balance. A large year-end build would otherwise make days outstanding look worse than the year’s typical stock level.
What period length should I use?
Use 365 for a year, 90 or 91 for a quarter, or the exact number of days in the accounting period. COGS must cover that same span or the day count will be wrong.