Days of inventory (stock cover)

Days of inventory, also called stock cover or weeks of cover, is how many days your current stock lasts at your recent selling rate.

By Berend Vrakking, founder of Product Metrics. Updated 7 October 2026.

Formula

Days of inventory = inventory on hand ÷ average daily units sold

Divide the days by 7 for weeks of cover. Average the daily units over a recent period you name, such as the last 28 days.

Example

Worked example, average over the last 28 days
Product	On hand	Units sold per day	Days of inventory
Trail Runner 2	700	10	70 days (10 weeks)
Winter Boot	500	2	250 days
Both products	1,200	12	100 days

On paper the pair has 100 days of cover. In practice Trail Runner 2 sells out on day 70 while Winter Boot settles in for 250. Illustrative data.

For one product, and for an account

The number earns its keep next to supplier lead time: if a product’s cover is shorter than the time its supplier needs to deliver, you already know how the month ends. An account-level figure blends the fast sellers with the products that barely move and describes neither.

In Product Metrics, stock cover is shown per product in Inventory Insights. It feeds Product Score and reaches Merchant Center as a custom label you approve, so products you cannot deliver lose priority.

Common mistake

Using one sales rate for every product. A recent average misleads when demand is rising, falling or seasonal, so read the number next to the product’s trend.

Questions

How do you calculate days of inventory?

Divide the units you have on hand by the average units sold per day. With 700 units on hand and 10 units sold per day, you have 70 days of inventory, or 10 weeks of cover.

What does days of inventory in hand mean?

It is the number of days your stock on hand would last if it kept selling at your recent rate. It is not a promise: a change in demand or a late delivery changes the real date you run out.

What is stock cover?

Stock cover is another name for days of inventory, usually counted in weeks. A product with 16 weeks of cover has enough stock for 16 weeks at its current selling rate.

Keep reading

Inventory InsightsSee stock cover, reorder dates and slow stock per product.
StockoutWhat happens when the cover reaches zero before the restock.
Lead timeHow long a supplier needs to deliver, to set against your cover.
Reorder pointThe stock level at which to order, worked back from demand.
Custom labelsHow stock cover reaches your Google Shopping campaigns.
Dead stock inventory: how to find it and clear itUse stock cover and days since the last sale to find dead stock.