Quick answer
How do you calculate Days Inventory Outstanding?
Use Inventory days = Average inventory / Cost of goods sold x Days in period. Enter the matching values above to calculate the result instantly.
What it measures
Understanding Days Inventory Outstanding
Estimate how many days of cost of goods sold are held in average inventory. Inventory days translates turnover into time, helping teams compare stock investment with lead times, seasonality, and service targets.
Interpretation
What the result means
The result estimates the number of days represented by average inventory at the period's cost-of-goods-sold rate.
Action
How to use it
Review by product class and pair the metric with stockouts, aged stock, supplier lead time, margin, and demand variability.
Limits
What it leaves out
Averages can hide seasonal peaks, and accounting valuation, write-downs, acquisitions, or rapid growth can distort the estimate.
The math
Days Inventory Outstanding formula
Worked example
Example calculation
- Calculation
- $120,000 / $720,000 x 365
- Result
- 60.83 inventory days
Step by step
How to use this calculator
- 1Enter average inventory, cost of goods sold, days in period.
- 2Keep every input on the same time period and measurement basis.
- 3Review the result, then change one assumption at a time to test scenarios.
Decision support
When this calculator is useful
- Working-capital planning
- Stock policy reviews
- Supplier planning
Common questions
Frequently asked questions
Which inputs should I use for Days Inventory Outstanding?
Use average inventory, cost of goods sold, days in period, measured from the same source and period. Include only values that match the definitions shown beside each field.
Why might two Days Inventory Outstanding calculations differ?
The systems or accounting policies may define average inventory, cost of goods sold, days in period differently. Compare the time period, scope, source, and treatment of exceptional items before comparing results.
How often should I recalculate Days Inventory Outstanding?
Recalculate when any input changes materially and on the same reporting cadence used for the decision. Save the source and date of each input so the trend remains comparable.
Can I use Days Inventory Outstanding by itself?
No single metric captures the full decision. Use the result with the related measures, assumptions, and limitations shown on this page.
Calculation reviewed: 2026-06-18. CalcPilot uses the formula shown above and tests representative values during the production build. See our methodology and correction policy.
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