How to use this calculator
- Enter average inventory, cost of goods sold, days in reporting period.
- Choose a display currency, then select Calculate. Results also update after a brief pause while you edit.
- Read the result with the assumptions below. Export details or save a second scenario to compare your choices.
Formula and method
Assumptions and limitations
Use averages covering the same reporting period and the same cost or sales basis. These are descriptive averages, not invoice due dates.
Worked example
With average inventory = 10000, cost of goods sold = 100000, days in reporting period = 365, inventory days is approximately 36.5.
What the result means
Average time inventory remains on hand, valued consistently at cost.
Common questions
How should I interpret inventory days?
Average time inventory remains on hand, valued consistently at cost.
What should I check before using this result?
Use averages covering the same reporting period and the same cost or sales basis. These are descriptive averages, not invoice due dates.
Methodology and transparency
Calculation specification reviewed on 2026-10-14. Mathematical implementation is tested against independent reference fixtures. This does not imply review by a licensed financial professional. Read the testing and precision policy.
Background reference: openstax.org — financial method. FinanceMath implements its own calculator.