Amazon Storage Fee Calculator

The maths behind it

Monthly storage is charged on the average daily volume your inventory occupies: fee = average cubic feet × the monthly rate for the size tier and the season.

Rates rise sharply for the October to December quarter, typically around three times the off-peak rate, because warehouse space is scarcest when demand is highest.

Putting numbers to it

The small standard product measuring 9 × 6 × 2 inches is 108 cubic inches, or 0.0625 cubic feet. At an off-peak rate around $0.78 per cubic foot that is $0.049 a unit a month; call it $0.09 including the practical overheads of how space is measured.

Holding 3,000 units costs roughly $146 a month off-peak and around $440 a month in the fourth quarter.

Across a year with three peak months, storage on that inventory is about $2,630: against $151,950 of revenue at 1,000 units a month. Under 2%, which is why storage is easy to ignore until stock stops moving.

Where it is unreliable

Storage is trivial on fast-moving stock and punitive on slow-moving stock, and the average across a catalogue hides that completely. A product with twelve months of cover pays twelve times the storage of one with a month, on the same unit.

The fee is also charged on average daily volume, so a large delivery arriving on the first of the month costs far more than the same delivery arriving on the twenty-eighth.

How to act on this

Time inbound shipments so stock arrives close to when it is needed rather than well ahead, particularly going into the fourth quarter. Arriving in late September rather than early October is worth a third of a quarter's peak storage.

Then look at storage per unit sold rather than storage in total. That figure identifies the slow movers immediately, and it is the ones with high storage per sale that are quietly eroding the account's margin.

Storage as the early warning on a failing product

Storage cost per unit sold is one of the cleanest indicators of a product that is not working. A healthy product carries a few cents; a failing one carries dollars, because the same stock is being charged month after month against a shrinking number of sales.

It also compounds: as sales slow, cover extends, storage per sale rises, and eventually the aged inventory surcharge arrives on top. A product that stalls in January can be paying multiples of its original storage by August without anyone deciding anything.

The discipline that prevents it is a monthly review of cover by SKU with a rule attached: anything above a threshold gets a price action, an advertising push, or a removal decision. Making that decision at four months of cover costs a markdown; making it at ten costs the markdown plus a year of storage plus the surcharge, and by then the stock is worth less anyway.

The other timing lever is removals. Because storage is charged on average daily volume, removing dead stock early in a month saves most of that month's charge, while removing it on the twenty-eighth saves almost nothing, a distinction worth knowing when a removal decision has already been made.