Estimate whether an FBA product may be exposed to Amazon's low-inventory-level fee, how many units could restore 28 days of cover, and when replenishment needs to leave.
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At the current forecast, shipment lead time leaves approximately 0 days before cover would approach the target. This is a planning estimate, not Amazon's fee determination.
Where the orange line crosses the dashed red line is when current cover would drop below 28 days — replenishment needs to be checked in before that point, not merely shipped.
Amazon's low-inventory-level fee is based on historical days of supply rather than only the units visible today. Under the published framework, the fee generally applies when both the short-term and long-term historical metrics are below 28 days, subject to eligibility rules, product scope, and exemptions.
Enter the historical values shown in Seller Central. The calculator does not recreate Amazon's proprietary metric from raw inventory events.
Current days of cover divides available and inbound units by forecast daily demand. It helps with replenishment timing, but it can differ from Amazon's 30- and 90-day historical calculations.
Sending inventory today may improve future short-term supply, yet receiving delays and historical measurements mean it may not eliminate a fee immediately.
Ordering enough to clear 28 days is not automatically optimal. Include supplier lead time, seasonality, sales volatility, storage, aged-inventory exposure, cash constraints, and inbound receiving time.
Use the restock forecast for a longer projection and confirm actual fee eligibility in FBA Inventory.
The low-inventory-level fee is a per-unit surcharge added to the FBA fulfillment fee on each unit shipped to a customer while the product is below the threshold — not a one-time penalty. That structure has an uncomfortable property: the fee is largest exactly when a product is selling well on thin stock, because every one of those sales carries the surcharge.
Under Amazon's published framework, the charge is tiered: the further your historical days of supply fall below 28, the higher the per-unit rate, and rates also scale with the item's size tier and weight. Illustratively, the structure looks like this (confirm current rates for your marketplace in Seller Central — they change):
| Historical days of supply | Fee behavior | Practical read |
|---|---|---|
| 28 days or more (either metric) | No fee | Keeping either the 30-day or long-term metric at 28+ is sufficient to avoid the charge |
| 21–27 days | Lowest fee band | A warning zone — cheap to fix if replenishment is already moving |
| 14–20 days | Middle band | The fee is now compounding with every sale; expedite if the gap to your next receiving date is long |
| 0–13 days | Highest band | You're paying the maximum surcharge on your best-selling days — often the point where air-freighting a top-up beats waiting for ocean |
Because the metric is historical (a trailing 30-day and long-term view), it lags reality in both directions: stock arriving today doesn't clear the fee immediately, and a sudden sales spike can pull you into fee territory even though yesterday's dashboard looked fine.
Not every low-stock situation is charged. Amazon has published several exemptions, which have included:
The exact list, thresholds, and grace-period lengths have changed since the fee launched, so treat the exemption checkbox in this calculator as "I have verified my exemption in Seller Central," not as a guess. The authoritative view is the fee-preview column in your FBA Inventory page and the low-inventory-level fee report under Payments.
No. Amazon uses historical short- and long-term metrics and applies program rules and exemptions.
Review the relevant FBA Inventory views and fee reports in Seller Central.
No. Product eligibility and exemptions can apply. Confirm the current rules for your marketplace and account.
It's a tiered per-unit surcharge on the fulfillment fee — commonly in the range of a few tens of cents to around a dollar per unit shipped, rising as historical days of supply fall further below 28 and with larger size tiers. Check the current rate card in Seller Central; enter your product's actual rate in the fee-per-unit field above.
Amazon has published exemptions for new sellers during an initial grace period and for recently launched new-to-FBA products, plus very low-velocity items. Thresholds and windows have changed over time, so verify your specific product's status on the FBA Inventory page rather than assuming.
Usually not. The metric is a trailing historical calculation, and inbound units don't count until received and checked in. Expect the fee to persist for days to weeks after replenishment arrives, which is why acting before the metric crosses 28 is much cheaper than reacting after.
Within reason, yes — the comfortable operating zone for most SKUs is roughly 30–45 days above the threshold. But overshooting into 90+ days trades this fee for monthly storage and eventually aged-inventory surcharges, so the target is a band, not a maximum.
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