Estimate how many days current usable inventory can cover at an assumed daily demand rate.
Days of Supply Calculator
Formula
Days of supply = usable inventory ÷ average daily demand
How to use the result
Use usable, available stock rather than including quarantined, damaged or otherwise unavailable inventory.
What the calculator does not know
These tools are general inventory-planning aids, not accounting, tax, regulated-product, hazardous-material, food, pharmaceutical or safety-stock policy advice. Requirements for controlled, perishable or safety-critical inventory can be materially different; use applicable regulations, contracts, manufacturer requirements and qualified professional guidance.
Improve the estimate
Keep the inputs used for the decision and compare the estimate with actual results. A simple calculator is most useful when it makes the assumptions visible enough to learn from the difference.