Amazon FBA · inventory planning
Inventory runway, without a black box.
Turn the units sold in a period into an average daily run rate, then see available and inbound days of cover.
Days of cover = available units ÷ units sold per day. Reorder point = daily units × (lead days + safety days). No seasonality or demand model is added.
Inventory and sales
Straight-line plan
Method and data boundaries
Shopify defines days of inventory remaining as ending inventory units divided by inventory units sold per day. This page applies the same disclosed arithmetic to the FBA counts you enter. Amazon states that inventory reports are snapshots and may become stale as customers buy, so refresh your FBA numbers before acting. Inbound stock is shown separately because arrival timing is not guaranteed by this calculation.
Official sources, checked 15 October 2026: Shopify analytics fields: days of inventory remaining and Amazon: Download an inventory report.
FAQ
Does this forecast future demand?
No. It divides current stock by the historical daily run rate you supplied.
Does inbound inventory delay the order date?
The page shows inbound-inclusive cover, but the reorder point uses available stock because transit and receiving timing are outside this calculator.