How Amazon FBA storage fees are calculated
Monthly storage is charged on the volume your inventory occupies, not on the number of units or their value. The formula is straightforward:
Monthly storage fee = Cubic feet per unit × Units stored × Rate for size tier and season
Cubic feet per unit is length × width × height in inches, divided by 1,728. Amazon measures the packaged unit, not the product, so packaging that adds half an inch in each direction can cost real money at volume.
2026 monthly storage rates
The peak rate is the part that catches people out. Standard-size storage costs roughly three times more from October through December — exactly the months when most sellers hold their largest inventory position. A Q4 plan built on the $0.78 rate will understate storage cost by about 200%.
A worked example
1,000 units of a standard-size product measuring 9 × 6 × 3 inches. Volume per unit is (9 × 6 × 3) ÷ 1,728 = 0.094 cubic feet, so 1,000 units occupy 93.75 cubic feet.
Note that three peak months cost slightly more than nine off-peak months. Any conversation about reducing storage cost is really a conversation about Q4 — we break the whole quarter down in what Q4 inventory really costs.
Storage is not the only inventory charge
Monthly storage is the baseline. Two further charges apply to stock that sits too long, and both are far larger. If neither is worth paying, the alternative is removal or disposal:
Practical ways to reduce storage cost
- Shrink the box, not the product. Storage is priced on volume. Cutting one inch off each dimension of a 9 × 6 × 3 unit removes roughly 40% of its cubic footage — and 40% of its storage bill — without touching the product itself.
- Time your Q4 inbound. Stock arriving in late September pays peak rates for three full months. Arriving in mid-October often costs less overall, provided you can accept the stockout risk.
- Watch the units that never sell. Storage is charged on everything, including the SKUs contributing nothing. Slow movers are usually a bigger share of the bill than sellers expect — a dead-stock view makes it obvious.
- Reorder to demand, not to a schedule. Sending twelve months of stock to save on freight often costs more in storage than it saves. The restock calculator sizes the order properly.
This calculator estimates one SKU at a time. To see storage cost charged against every SKU in your actual P&L — and which products are quietly consuming it — SellerGuards pulls your real inventory and fee data from Amazon's SP-API.