FBA Inventory Placement Optimizer

How to use this calculator

How the placement maths works

Every unit you own has to live somewhere, and the three options charge differently. FBA charges rent per cubic foot per month, with a peak rate from October to December and surcharges that punish both understocking and overstocking. AWD charges a flat storage rate all year, plus a one-time cost each time a unit moves into FBA. A 3PL charges storage plus pick-and-pack on every unit that leaves. The calculator compares the three over one common horizon — the months your total stock lasts at current sales — with each location's storage charged on its average volume as the buffer drains, and the one-time handling costs spread over the same horizon. That is the only way the comparison is honest: a buffer that empties in two months should not be priced as if it sat full all year.

The target is a corridor, not a single number. Keep roughly 30 days of cover in FBA: comfortably above the 28-day line where the low-inventory-level fee starts, and far below the 22-week line where the storage utilisation surcharge starts. Hold the next 60 days in AWD if the maths supports it, and the rest at a 3PL. When FBA is cheapest and it fits your capacity limit, the tool says so — the split only wins when capacity, surcharges or Q4 rates make FBA the expensive option.

Four fees that punish the wrong placement

The low-inventory-level fee punishes running too lean. When a SKU's days of supply falls below 28 days in both the trailing 30-day and trailing 90-day windows, Amazon charges a per-unit fee on units shipped — from $0.32 to $2.09 per unit depending on size class and how thin the cover is. Below 14 days pays the highest band. Grocery products are exempt, and so are slow movers and products with fewer than 20 units shipped in the last 7 days.

The storage utilisation surcharge punishes holding too much. When your utilisation ratio — average daily inventory volume divided by average daily shipped volume over the trailing 13 weeks — passes 22 weeks of cover, Amazon adds $0.44 to $1.88 per cubic foot on standard-size (and $0.23 to $1.26 on oversize) on top of base storage. It applies to Professional sellers whose first FBA shipment was more than 365 days ago, averaging at least 25 cubic feet per day in a size tier, and only to inventory older than 30 days.

The aged inventory surcharge punishes holding too long. Past 181 days, Amazon adds a second per-cubic-foot charge that steps up through age bands — $0.50 at 181–210 days, $1.50 at 241–270, then a cliff to $5.45 at 271–300 days and up to $7.90 past 456 days (or a per-unit minimum, whichever is greater). Clothing, shoes, bags, jewelry and watches skip the 181–270 bands entirely and start at $5.45 on day 271. The surcharge is assessed from a snapshot on the 15th of each month.

Capacity and IPI punish both at once. Your FBA capacity limit is a monthly cubic-foot allocation set from your IPI score, sales forecasts and network conditions — exceeding it blocks new shipments rather than billing you. The old $10 per cubic foot overage fee was eliminated in July 2024. Most 2026 guides report the IPI threshold as 400, some as 350; this tool lets you edit it. Falling below it tightens your limit and can stop new shipments, but it does not by itself trigger a surcharge — the surcharge is driven by weeks of cover, not by IPI.

The 2026 rate tables this tool uses

The rates below are the 2026 US schedule, verified 12 November 2026 against Amazon's published fee pages and multiple independent guides that cite them. Amazon revises them in its annual fee updates, and your Seller Central account shows the rates that actually apply to you. Check them against Seller Central's monthly inventory storage fees page; where a rate here and your account disagree, your account is right.

AWD also charges $1.40 per box inbound processing, $1.40 per box outbound processing and $1.40 per cubic foot for transportation into FBA (10% off both storage and transport on the Smart Storage rate, 20% off storage and transport at $1.26 per cubic foot on the Amazon Managed rate). The Capacity Manager performance credit is $0.15 for every $1 of sales generated using additional capacity.

Worked example — the calculator's default numbers, so you can reproduce every figure: 2,000 units at 0.19 cu ft each (380 cu ft total), selling 10 a day at $25, standard-size, January–September, 300 units in FBA against a 100 cu ft limit, IPI 450, AWD auto-replenishment on at a 70% ratio in the East region, 3PL at the $0.65 / $2.50 defaults. The stock lasts 200 days (6.67 months). FBA: 30 days of cover, 300 units, 57 cu ft × $0.78 = $44.46 a month. AWD: 60 days, 600 units — Smart Storage applies (70% ratio, 200 days combined cover), so $0.43 per cu ft on an average 57 cu ft for two months is $49.25, plus $243.60 of one-time transfers ($0.41 per unit), totalling $292.85 over the horizon = $43.93 a month. 3PL: 1,100 units — storage $249.06 on an average 104.5 cu ft over 110 days, plus $2,750 of pick-and-pack, totalling $2,999.06 = $449.86 a month. Cheapest split: $538.25 a month. All-in-FBA would be $292.60 a month (average 190 cu ft at $0.78, plus a $0.76 utilisation surcharge at 28.6 weeks of cover) — but your 100 cu ft limit blocks it, 280 cu ft over. The capacity limit is costing $245.65 a month against the all-in-FBA ideal, and skipping AWD entirely (FBA + 3PL only) would cost $771.19 a month. A Capacity Manager bid of $0.30 per cu ft on the 280 cu ft overflow is an $84.00 reservation fee, breaking even at $560 of sales — about 2.2 days at current velocity, against $1,125 of performance credits over 30 days.

How to cut the 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 actual weekly sales. Smaller, more frequent replenishment usually costs less in total than one deep shipment once storage and surcharges are counted. Keep FBA inside the corridor. Thirty to sixty days of cover in FBA stays above the low-inventory fee and below the utilisation surcharge; drift either way and a fee starts. Stage the buffer in AWD, not FBA. AWD storage is flat all year, does not count against your capacity limit, and with auto-replenishment at a 70% ratio it waives the low-inventory, utilisation and aged fees on the SKU — but size the AWD buy to real forecasted demand, or you have only moved the overstock problem upstream. Deal with aged stock before day 271. The surcharge jumps from $1.50 to $5.45 per cubic foot at 271 days; discount, bundle or remove the aging tail while it is still in the cheap bands, and time clearances to complete before the 15th, when the monthly snapshot is taken. Plan around Q4. Peak storage triples standard-size rent, so inventory that will not sell until January should not arrive in October — and AWD's flat rate is worth most exactly then. Finally, bid for capacity only on stock that sells. A Capacity Manager reservation fee is fully offset when the extra space generates enough sales; on slow stock it is just another bill.

FBA Inventory Placement Optimizer: what this tool models

This FBA vs AWD calculator models one SKU's storage and handling across three locations — FBA, Amazon Warehousing & Distribution and a 3PL — using the 2026 US fee schedule. It compares the cheapest feasible placement split against all-in-FBA and against FBA-plus-3PL, diagnoses the four fees your current position triggers (low-inventory-level, storage utilisation, aged inventory, and the capacity/IPI block), tests the 70% auto-replenishment exemption, and works out the Capacity Manager bid break-even at $0.15 of performance credit per $1 of sales.

What it deliberately does not model: referral and fulfillment fees (use the FBA profit calculator for per-unit margin), FBA inbound placement fees on shipments sent from a 3PL, and removal or liquidation charges. The 3PL rates are your quote to enter, not ours to guess — a real 3PL quote always beats a generic default. Run the numbers before you buy inventory, before you change a price, and every quarter, because Amazon revises this schedule and the 2027 changes land on 1 February 2027. Our Amazon FBA fees guide walks the whole fee stack behind these numbers.