Amazon FBA Storage & Aged Inventory Surcharge Calculator

How to use this calculator

How FBA storage fees actually work

Amazon charges FBA storage by the cubic foot, not by the unit or the pound. Your item's packaged dimensions are converted into cubic feet, multiplied by every unit you have in the fulfillment network, and billed monthly based on your average daily volume. Two consequences follow. First, small-but-slow products are the worst deal in FBA: a featherweight item in a big box rents warehouse space at the same rate as anything else its size. Second, the fee is really two prices — a standard January–September rate and a much higher October–December peak rate, roughly two to three times as much, because space is scarcest in Q4. Standard-size and oversize inventory are also priced differently, with oversize cubic feet often cheaper per foot but belonging to items that occupy far more of them.

Storage also interacts with the rest of the FBA fee stack in ways the headline rate hides. Amazon can add a storage utilization surcharge for sellers holding a lot of volume relative to their sales, and a separate low-inventory-level fee punishes the opposite mistake — running too lean. The practical target is a corridor: enough stock to stay in the Buy Box, never so much that rent, surcharges and peak rates eat the margin. Storage is easy to ignore because no single month looks dramatic; model it per unit, over the real number of months stock will sit, and it stops being a rounding error. Our Amazon FBA fees guide walks the whole fee stack, and the FBA profit calculator folds storage into a full per-unit margin.

Aged inventory: rent with a penalty on top

Once a unit has been in a fulfillment center for more than 181 days, Amazon stops charging only rent. The aged inventory surcharge adds a second per-cubic-foot monthly charge on that aged stock, and it steps up through age bands — inventory past 271 days costs more than inventory at 190 days, and the oldest bands cost many times the first. The surcharge is assessed on the volume of the aged units, on top of the normal monthly storage fee for the same space. A product can therefore move from "slow but fine" to "paying double rent" without anything changing except the calendar.

This is why the calculator separates the two charges and asks what share of your units is aged. Aged share is the number most sellers never compute: a listing can show healthy overall sell-through while its oldest 15–20% quietly accrues penalties every month. The fix is rarely dramatic — discount or bundle the aging tail before it crosses the next band, run a removal order on stock that will never sell at full price, or feed it into an outlet or liquidation channel. A small, deliberate margin cut at day 150 beats months of surcharges followed by a removal fee at day 300, when you pay to get back stock you have already paid to store. And before you reorder anything, run the replacement quantity through the break-even calculator: if the new batch only works at a volume that guarantees an aged tail, the product — not the storage — is the problem.

Example rates and a worked example

The rates below are the examples this calculator is prefilled with, based on publicly reported Amazon schedules. They are labeled examples, not a quote — Amazon revises them, and your Seller Central account shows the rates that actually apply to you. Check them against Seller Central’s monthly inventory storage fees page and your own storage report; where an example and your account disagree, your account is right.

A different worked example \u2014 invented round numbers, same example rates: a board game in a 10 \u00d7 10 \u00d7 3 in box is 300 cubic inches, which is 0.1736 cubic feet per unit. Eight hundred units occupy 138.89 cubic feet, renting at the standard January\u2013September example rate of $0.87 for $120.83 a month \u2014 $362.50 over three months. If 25% of those units cross 181 days, their 34.72 cubic feet draw the example $0.50 aged inventory surcharge for one month: $17.36. Period total: $379.86, about $0.47 per unit. And if that same stock sits into Q4 instead, the peak $2.40 rate makes the rent alone $333.33 a month \u2014 the calendar, not the product, did that.

How to cut your FBA storage bill

Match inbound depth to sell-through. Most storage waste is bought, not stored: order quantities set by supplier MOQs and optimism rather than by your actual weekly sales. Smaller, more frequent replenishment usually costs less in total than one deep shipment once storage and surcharges are counted. Review aged inventory every month. Seller Central's aged inventory report shows exactly which units approach the next surcharge band; act on the oldest first with price cuts, coupons, bundles or ads while they are still sellable. Remove what will never move. A removal or liquidation fee is a one-time cost; storage on dead stock is a monthly subscription to a loss. Keep buffer stock out of FBA. Holding reserve inventory at a third-party warehouse — or in Amazon Warehousing & Distribution — and feeding FBA in smaller waves keeps your FBA footprint close to what you will sell this month, which is the volume your storage bill should be based on. Finally, plan around Q4: peak storage rates mean inventory that will not sell until January should not arrive in October.

Amazon FBA storage fee calculator: what this tool models

This Amazon FBA storage fee calculator models the two charges separately, because they behave differently. Monthly storage is rent: a per-cubic-foot charge on everything you hold in Amazon fulfilment centres, at standard rates from January to September and peak rates from October to December. The aged inventory surcharge is a penalty layered on top, charged only on stock that has sat past Amazon's age thresholds — the longer it sits, the more it costs.

Keeping the two apart matters because the fixes are different. Rent is controlled by how much you ship in and how fast it sells. The surcharge is controlled by how you deal with the oldest units at the back of the bin: price moves, removal orders or disposal before the next age threshold lands. Enter your figures above and look at which half of the bill is yours.