Amazon Stockout Report: Days Below Cover Are Not Days at Zero

An Amazon stockout report counts the days a product was out of stock, but "out of stock" can mean two different things: days when sellable stock was at zero, or days when stock sat below a set level, such as three weeks of sales. As long as the level is above zero, the second count can never be smaller than the first, and the gap can be wide. Before you act on a stockout report, find out which definition it uses, then look at both numbers.

When we ran an out-of-stock report on our own brand's account (as of October 26, 2026), one product showed 42 days below the level and 9 days at zero over the same 90 days. Below: what each definition measures, how to rebuild both counts from Amazon's Inventory Ledger, a worked example, what we saw in our own report, and where the usual stockout advice breaks.

What an Amazon stockout report actually counts

Whether you call it a stockout report or an out-of-stock report, it counts days, and the definition of a stockout day decides the number. You will meet three definitions:

1. Days at zero. Sellable stock was zero, so the product had nothing to sell from that pool. This is the number behind lost sales.
2. Days below a level. Stock was under a threshold, set in units or in days of cover (stock divided by daily sales). The product may still have been selling; it was running thin.
3. Amazon's own low-stock measure. Amazon's low-inventory-level fee does not wait for zero either. As Amazon staff explained in the Seller Forums, the fee is based on historical days of supply over the last 30 days and the last 90 days, and it is charged only when both are below 28 days. Exemptions apply and Amazon updates these rules, so check the current terms in Seller Central.

Every count also depends on two quieter choices: which stock pool you count (sellable units only, one marketplace, units moving between warehouses or not) and which moment of the day you look at. A product that sells out at 3 p.m. ends the day at zero but sold for most of it.

How to pull stockout days from Amazon's Inventory Ledger

Amazon's Inventory Ledger report is the raw material for both counts; Amazon describes it as "like a bank statement of your inventory." Its Summary view, documented in Amazon's SP-API reference for FBA inventory reports, has columns that include Date, Disposition, Starting Warehouse Balance, In Transit Between Warehouses, Customer Shipments and Ending Warehouse Balance.

To turn it into a stockout count:

1. Request daily rows. Through SP-API, the Summary view aggregates by month unless you ask for weekly or daily data, and a monthly row cannot tell you how many days inside the month were at zero.
2. Keep the country view. The report aggregates by country by default and can also be split by fulfillment center. A zero in one building is not a stockout if another building still has the product.
3. Keep only sellable stock. Filter Disposition to the units you can sell; damaged or defective units do not fill orders.
4. Pick the moment of the day. Use Starting Warehouse Balance to count days that began with nothing, or Ending Warehouse Balance to count days that ended with nothing. Decide whether units in transit between warehouses count for you; the ledger keeps them in their own column.
5. Count the days at zero. That is your days-at-zero number.
6. Count the days below your level. Divide each day's balance by daily sales velocity to get days of cover, and count the days under your level. That is your days-below-level number.

Write down the level, the velocity window and the moment of the day you used. Next month's count is only comparable if those stay the same.

Worked example: one SKU, two stockout numbers

Here is how the same 90 days produce two very different stockout numbers. The figures are illustrative round numbers, not data from any real account.

Say a SKU sells 10 units a day when it is in stock, and your level is three weeks of cover, or 210 units. Over a 90-day window, the daily ledger shows:

1. 30 days with sellable stock below 210 units
2. 6 of those days starting at zero sellable units

A report that counts days below the level says the SKU was out of stock for 30 days, a third of the window. A report that counts days at zero says 6 days, under 7 percent of it.

Now put each number to work:

1. Lost sales. At 10 units a day, 6 days at zero is about 60 units of missed sales. Run the same math on 30 days and you get 300 units, five times too high, because in this example the SKU kept selling on the 24 thin days.
2. Cleaning velocity. Over the window the SKU sold 840 units: 10 a day for the 84 days it was in stock. The raw 90-day average reads 9.3 a day. Drop the 6 days at zero and you get the true rate of 10. Drop all 30 days below the level and you land on the same 10 a day from a third less data.
3. Reorder timing. Here the below-level count is the useful one. The SKU spent a third of the window running thin, which says the reorder came late, even though it hit zero on only 6 days.

The at-zero count measures the damage; the below-level count measures how often you were exposed. A report that gives you only one of them hides half the story. If a stockout dragged down the velocity behind your next order, here is how to set an Amazon FBA reorder point from actual lead times.

What we saw in our own stockout report

Our own report counted days below a level as days out of stock. When we ran the out-of-stock tool of Propamp's MCP server on our own brand's account (as of October 26, 2026; US marketplace, all products, a 90-day window ending October 25, 2026), we saw this:

1. The tool returned eight products. For each one it gave days out of stock, days below a stock level, days at zero, days above the level and a cover-days value of 14.
2. For all eight, days out of stock equalled days below the level. So the tool counted a day as out of stock whenever stock was under the level, not only when it was at zero.
3. Five products had days below the level, from 16 to 62. Their days at zero ran from 6 to 42.
4. On one of them the two numbers were far apart: 42 days below the level against 9 days at zero.
5. Two products had no days below the level, and one listing had no stock on any of the 90 days.

This is one account, one marketplace and one window. The response did not say how the level is set, and we did not check lost sales or other marketplaces. What it showed us is narrow but useful: ask which definition a stockout report uses, because days below a cover level and days at zero told different stories for the same product.

Where the usual stockout advice breaks

The usual advice breaks when it treats one definition as the whole story, or when the inputs behind a count shift without anyone noticing.

Counting only days at zero misses the thin weeks

A count of days at zero ignores weeks of low stock that can already cost you money. Amazon's low-inventory-level fee looks at historical days of supply, not at zero, so a product that keeps FBA stock thin between shipments can pay it without ever going out of stock. If your report counts only zero days, add a below-level count next to it.

Counting only days below a level overstates lost sales

A below-level count tells you when stock was thin, not when sales stopped. Use it for lost-sales math and, as the example showed, you can overstate the loss several times over. Use days at zero for lost sales and for cleaning velocity, and days below the level for reorder timing.

A days-of-cover level moves with the velocity window

If your level is set in days of cover, the count depends on the velocity you divide by. When we divided stock by sales velocity for seven stocked products on the same account (US marketplace, October 26, 2026), the 7-day velocity gave the product with the least cover about twice the days of cover that the 30-day velocity gave. One of the seven was under three weeks of cover on every velocity window; a second fell under three weeks only on a headline velocity that had no stated window. Pick one window, write it down and use it for every product, or the counts will not compare.

Listings with no stock all window skew the totals

A listing that had no stock on every day of the window counts as out of stock for all of it. Review such listings separately before you add up or average stockout days across the catalog, or one listing can outweigh the rest.

A stockout report looks back, not forward

A stockout report is history: it tells you where you ran out, not where you will. For the forward view, use days until stockout, which is current stock divided by daily velocity, and check it against what is already on the way.

Tracking stockout days in Propamp

In Propamp, the stockout history and the forward view sit in different places:

1. Out of Stock. The Out of Stock view shows how many days each product was out of stock. It is a historical count for spotting patterns, not an alert.
2. Restock Suggestion. Restock Suggestion shows days until stockout as current stock divided by velocity and ranks products as Critical, Urgent, Soon or Planned. You pick the velocity lookback, use the year-over-year option, or enter your own number, for example before a promotion.
3. Stock by location. The Stock Panel shows stock by location across FBA, FBM (fulfilled by merchant) and AWD (Amazon Warehousing and Distribution), including AWD on-hand and available units, so you can check which pool is running low.
4. Inventory health. Inventory health adds excess, stranded, days of stock and inventory age.
5. An AI agent. Through Propamp's Amazon MCP server, an AI agent such as Claude can read your synced inventory data and answer questions such as "which products were out of stock the most days last quarter?" Name the definition you want in the question, since an out-of-stock count can mean either one. Here is how to connect Claude to your Propamp data.

MCP (Model Context Protocol) access is included in the trial; on paid plans, outside AI clients need the MCP access add-on. Claude needs a Pro plan or higher.

Out of Stock and Restock Suggestion work on your history and on the velocity you choose. Propamp does not send stockout alerts and has no seasonal forecast, so the definition, the level and the window you pick still decide what the numbers mean.

Check your own stockout days

Start a two-week free trial (no credit card) from the Amazon inventory management page, connect Seller Central, and look at how many days each of your top products was out of stock. Then run the checks above before you decide whether the problem was an empty shelf or a thin one.

How we made this: drafted with AI assistance and checked against Propamp's public documentation, the sources linked above and our own brand's account (observations as of October 26, 2026).