Days of inventory is how long your current stock of a product will last at its current rate of sale. It is calculated by dividing units on hand by average daily units sold. For collection sorting, it tells you which products are about to run out and which are sitting on months of unsold stock.
Why does it matter for sorting?
It catches two opposite failure modes. A product with three days of stock left does not need promotion: it will sell out on its own, and giving it a top row wastes your best positions on inventory you cannot replace this week. Meanwhile, a product with 200 days of stock is quietly tying up cash and storage and needs visibility to move. Days of inventory turns both situations into a single sortable number.
How do you use it in a sorting recipe?
- Clearance collections: sort high days of inventory first, so overstocked products get the exposure they need to clear.
- Regular collections: add a modest weight so deep-stocked products get a nudge while sales signals still lead the order.
- Sellout protection: demote products with very few days left, or combine the signal with an out-of-stock inventory buffer that treats nearly-gone as gone.
We cover the attribute itself, including setup, in the days of inventory guide.
One caution
Days of inventory depends on a sales-rate estimate, so it is only as good as the window behind it. New products with little history produce unreliable values, and seasonal items can look healthier or sicker than they are depending on when you measure. Treat it as one weight among several, not the whole strategy.
Days of inventory is a built-in Dynasort attribute. Install it from the Shopify App Store or see how it works.