Amazon Low Inventory Fee Calculator
Days of cover, and the reorder point.
Days of cover, and the reorder point.
Amazon revises fee schedules at least annually and adds new surcharges more often. These defaults are a starting point, the figures in your own fee preview are the ones that describe your ASINs.
Days of cover
22 days
in the fee zone
Below roughly four weeks of cover the low inventory fee applies to every unit you sell, $115 a month here. With a 45-day lead time you need to reorder at 540 units of cover, not at zero.
How the Amazon Low Inventory Fee Calculator works
Amazon charges a fee when your cover falls below roughly four weeks, on the reasoning that thin stock makes its delivery promises harder to keep. It applies per unit sold, so it hits hardest exactly when you are selling well and running short.
Also known as: low inventory level fee · Amazon days of supply fee · FBA low stock charge
Setting it out
The low-inventory-level fee applies a per-unit charge when a product's historical days of supply falls below a threshold, on the basis that thin inventory forces Amazon to ship from fewer locations at greater cost.
It is assessed against a rolling measure of days of supply rather than a snapshot, so a brief dip may not trigger it and a sustained one will.
Cost = units shipped during the low-inventory period × the applicable per-unit fee.
A concrete case
The $29.99 product selling 1,000 units a month needs roughly 28 days of supply to stay clear of the threshold, about 950 units on hand at all times.
Falling to 400 units, roughly twelve days of supply, triggers the fee. At a rate around $0.32 a unit on 1,000 units shipped that month, the cost is $320.
Against $12,650 of monthly pre-advertising contribution that is 2.5%, not fatal, and entirely avoidable.
The larger cost is usually what caused the low inventory in the first place: a delayed restock, which risks a stockout, which costs rank, which costs far more than the fee.
What the number hides
The fee is triggered by days of supply rather than absolute units, so a product whose sales accelerate can fall below the threshold without the stock level changing at all. Growth causes it as reliably as poor planning does.
Restock limits can also make it difficult to avoid: a seller capped on how much they may send has less control over cover than the fee structure assumes.
Where to go from here
Manage FBA cover to a target above the threshold rather than to a stockout floor. The safety stock arithmetic from the inventory cluster applies directly, the threshold simply raises the target.
Then use a third-party warehouse as a buffer where restock limits or aging risk make holding everything at Amazon unattractive. Replenishing FBA weekly from reserve stock holds cover without the aged inventory exposure.
The tension between this fee and the aging surcharge
Amazon now charges for holding too little and for holding too much, and the window between the two is narrower than it looks: above roughly four weeks of cover to avoid the low-inventory fee, below roughly six months to avoid the aging surcharge.
For a product with steady demand that is a comfortable range. For a seasonal or volatile product it can be genuinely difficult, because the cover that is right in peak season is excessive out of it.
The structural answer is a two-tier inventory position: enough at Amazon to hold cover within the window, with the rest held elsewhere and fed in. It costs a handling fee per unit and it removes both charges, which for a product with any demand volatility is usually cheaper than optimising a single FBA position against two opposing penalties.
The threshold is measured against historical days of supply, so a product whose sales rate is accelerating can breach it while stock levels look healthy against last month's rate. Forecast-based cover, rather than trailing cover, is what actually protects against it.
Where to go next
The Amazon Low Inventory Fee question rarely arrives on its own. These are the ones that usually come with it:
- Reorder Point Calculator — The stock level that should trigger a new order.
- Amazon FBA Capital Requirement Calculator — Stock in the pipeline plus money awaiting payout.
- Amazon Inbound Placement Fee Calculator — Pay the fee or split the shipment yourself.
- Etsy Fee Calculator — Every Etsy fee on one sale, itemised.
Not financial advice. Marketplace fees change, and they vary by country, plan and seller status. Every rate here is an editable default, not a quoted price, check the platform's current fee schedule before you price a product against it. This is not tax or business advice.
Frequently asked questions
What triggers the low inventory fee?
Historical days of cover falling below the threshold, assessed against your recent sales rate. It applies to units sold while cover is low, not to units held.
How much cover should I hold?
Enough that your reorder point sits above the threshold given your lead time. With a ten-week lead time, reordering at four weeks of cover guarantees you spend six weeks paying the fee.
Why does it hit growing products hardest?
Because cover is measured against recent sales. A product that suddenly sells twice as fast halves its days of cover overnight, without a single unit leaving the shelf unexpectedly.
How do I avoid it?
Reorder against lead time plus safety stock rather than against a fixed unit count, and use a third-party warehouse to buffer so you can replenish FBA quickly without holding everything there.
Related calculators
Reorder Point Calculator
The stock level that should trigger a new order.
OpenAmazon FBA Capital Requirement Calculator
Stock in the pipeline plus money awaiting payout.
OpenAmazon Inbound Placement Fee Calculator
Pay the fee or split the shipment yourself.
OpenEtsy Fee Calculator
Every Etsy fee on one sale, itemised.
Open