---
title: "Days of inventory: formula and example | Product Metrics"
description: "Days of inventory, also called stock cover or weeks of cover, is how long your stock lasts at your recent selling rate. See the formula and a worked example."
canonical: "https://www.productmetrics.io/glossary/days-of-inventory"
pageType: article
language: en
publisher: "Product Metrics"
author: "Berend Vrakking"
datePublished: 2026-10-07
dateModified: 2026-10-07
---

> Content index: https://www.productmetrics.io/llms.txt

# 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.

## 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 Insights](https://www.productmetrics.io/inventory-insights): See stock cover, reorder dates and slow stock per product.
- [Stockout](https://www.productmetrics.io/glossary/stockout): What happens when the cover reaches zero before the restock.
- [Lead time](https://www.productmetrics.io/glossary/lead-time): How long a supplier needs to deliver, to set against your cover.
- [Reorder point](https://www.productmetrics.io/glossary/reorder-point): The stock level at which to order, worked back from demand.
- [Custom labels](https://www.productmetrics.io/glossary/custom-labels): How stock cover reaches your Google Shopping campaigns.
- [Dead stock inventory: how to find it and clear it](https://www.productmetrics.io/blog/dead-stock-inventory): Use stock cover and days since the last sale to find dead stock.

---

Written by Berend Vrakking, founder of Product Metrics. Last updated 2026-10-07.

HTML version: https://www.productmetrics.io/glossary/days-of-inventory