Amazon Long-Term Storage Fee Calculator

What the formula says

The aged inventory surcharge applies on top of monthly storage once units have been in a fulfilment centre beyond a threshold, currently starting at 181 days, with bands escalating sharply thereafter.

The charge is per cubic foot per month and is calculated on the units that have crossed each age band, so a single shipment can be paying several different rates at once as different portions of it age.

Written out: surcharge = aged cubic feet in each band × that band's rate, summed, and added to the ordinary monthly storage charge for the same units.

The numbers, worked through

3,000 units of the small standard product at 0.0625 cubic feet each is 187.5 cubic feet. Ordinary storage off-peak is around $146 a month.

If 1,200 of those units pass 181 days, the aged portion is 75 cubic feet. At a surcharge in the region of $0.50 per cubic foot per month that adds $37.50, and the bands escalate steeply past 271 and 365 days, where the rate can exceed several dollars per cubic foot.

By the time stock reaches a year, the combined storage and surcharge on that 75 cubic feet can run to several hundred dollars a month on inventory worth $10,200 at cost. Held for another year it would cost more than the goods.

That escalation is deliberate. Amazon is pricing warehouse space to force a decision, and the arithmetic makes holding indefinitely the worst available option by a wide margin.

What the number leaves out

The age clock runs from when the unit arrived at the fulfilment centre, not from when you bought it or when the shipment was created. Units sitting in an inbound queue or held at a receiving centre may age differently from what a seller assumes.

The surcharge is also assessed on a snapshot date each month rather than continuously, so units removed just before the assessment avoid it entirely and units removed just after pay a full month.

Sellers who plan removals by calendar month rather than by the assessment date frequently pay a charge they had already decided to avoid.

Turning it into a decision

Run an inventory age report monthly and act at around 120 days rather than 180. Once the surcharge starts, the product is already in the position where every option is worse than the one available two months earlier.

The options in order of preference: a price reduction to clear, an advertising push if the product converts, a multipack bundle to move units faster, removal to a third-party warehouse, and disposal last.

Disposal is not failure. Paying $0.32 a unit to dispose of stock that would otherwise cost $2 a year in storage and surcharge is straightforwardly the right decision, and the reluctance to take it is what turns a small loss into a large one.

Why the surcharge exists and what it tells you

Amazon's fulfilment network is optimised for throughput, and slow-moving inventory occupies space that fast-moving inventory would turn several times over. The surcharge prices that opportunity cost back to the seller.

For the seller, the useful signal is that any product reaching 181 days has failed a test that had nothing to do with fees. It did not sell at the rate the buying decision assumed, and the surcharge is the consequence rather than the problem.

The diagnostic worth running when it happens is which assumption was wrong: the demand forecast, the price, the listing quality, or the competitive position. Removing the stock solves the fee; understanding which assumption failed is what stops the next product doing the same thing. Sellers who treat aged inventory purely as a logistics problem tend to accumulate it repeatedly.