What this Amazon FBA calculator works out
Per-unit profit on Amazon US, with the whole fee stack rather than the two everybody remembers. Referral fee and FBA fulfilment fee are the obvious ones. The rest is where the money quietly goes:
- Monthly inventory storage, multiplied by how long a unit actually sits in the warehouse
- FBA inbound placement service fee — an official range, not a single number, so it shows as a range
- Overmax handling on items over 96 inches on the longest side or 130 inches in length plus girth
- Returns processing — charged on every apparel return, and above a category threshold for everything else
- Removal or disposal of the units that never sell, amortised over the units that do
- Import duty, additional tariffs, Merchandise Processing Fee, Harbor Maintenance Fee, and first-leg freight
The referral fee has two different shapes, and mixing them up is expensive
Amazon writes some categories as the portion of total sales price up to $X, and others as items with a total sales price up to $X. Those read almost identically and behave completely differently.
Compact Appliances is the first kind: 15% on the first $300 and 8% on everything above it. A $350 sale pays $49.00 — the rate steps, the fee stays smooth.
Clothing and Accessories is the second kind: the whole price is charged at the rate its band lands in. A $15.00 sale pays 5%, which is $0.75. A $15.01 sale pays 10% on the entire $15.01, which is $1.50. One cent of extra revenue costs you $0.75 in fee.
A calculator that implements one shape and applies it to both is out by more than 80% near those thresholds. This one keeps the two apart, and the results page shows which rule your category uses.
Duty is not landed cost times a rate
The United States assesses import duty on the transaction value of the goods — the price you pay your supplier — not on what it cost to get them here. Freight and insurance come out of the base before duty is applied, provided they are separately identified on the invoice.
The difference is not a rounding error. On a $12,000 CIF shipment carrying $1,800 of freight and $200 of insurance, customs value is $10,000. At 3.4% that is $340 of duty. Multiplying the full $12,000 by the same rate gives $408 — twenty percent too much.
Two more federal fees ride along, and both have rules that get flattened elsewhere. The Merchandise Processing Fee is 0.3464% of customs value but never less than $33.58 or more than $651.50 per entry — so it has to be worked out for the whole shipment and then divided by units. Divide the value first and every single unit hits the floor, which on a 500-unit shipment overstates the fee by a factor of 500. The Harbor Maintenance Fee is 0.125% and applies to ocean arrivals only; air and truck entries pay nothing.
Most fee surprises come from the size tier, and that means dimensional weight
The fulfilment fee is looked up by size tier, and the tier is decided by whichever is greater: the unit weight, or the dimensional weight — length × width × height ÷ 139. Dimensional weight is also called volumetric weight; the two are the same thing under different names.
That is why a light but bulky product costs far more to ship than its weight suggests, and why shaving an inch off a box sometimes drops the fee by a whole band. The results page shows both weights and says which one governed, so the tier is never a black box.
On top of the tier, the fee depends on the sale price band (under $10, $10 to $50, over $50), the season, and a fuel and inflation surcharge that is currently 3.5%.
What this tool does not know
A calculator that never admits a limit is not being careful — it is hiding something. These are ours:
- It does not look up HTS codes. The duty rate is one you supply, and the results page labels that line as yours rather than implying we found it.
- Fulfilment fees for bulky and extra-large tiers have a known discrepancy against Amazon’s own Revenue Calculator — measurements show ours coming out roughly $1.50 to $3.00 per unit low, which flatters profit. Any product in those tiers gets a warning saying so. Standard sizes have been checked against the Revenue Calculator item by item and agree.
- It covers Amazon US only. No VAT, no UK or EU marketplaces — and VAT is not a matter of adding another rate, because it is reclaimable and treating it as a cost would badly overstate what you pay.
- Lithium battery and low-inventory-level fees are not implemented. The de minimis exemption is deliberately left out: it has been narrowed repeatedly by executive order and building it in would produce a confidently wrong answer.
Common questions
- Why is my profit lower here than in Amazon’s Revenue Calculator?
- Because Amazon’s calculator answers a different question. It shows what Amazon charges you. This shows what you actually make, which also means paying for the goods, getting them to the United States, clearing customs, advertising the listing and taking returns. On an imported product the gap is usually most of the duty, the first-leg freight and the advertising.
- Do I have to fill in the import section?
- Only if the goods come from overseas. Leave it off and the calculator says so explicitly rather than silently returning zero for duty, MPF, HMF and first-leg freight — a zero because you skipped an input looks exactly like a zero because the cost does not apply.
- What are the three scenarios for?
- Freight, advertising and return rates cannot be known in advance, so they are entered as ranges. Conservative takes the unfavourable end of every one of them, optimistic the favourable end. Fees that come from published rate tables do not move between scenarios — only the genuinely uncertain parts do, which is why the three columns differ by exactly the amount you do not know.
- Does it include storage for slow-moving stock?
- Monthly storage is multiplied by the turnover months you enter, so slow stock costs more. Dead stock is separate: enter a dead-stock rate and the removal or disposal cost of the units that never sell is amortised across the units that do, using d ÷ (1 − d) rather than d — the money sunk into unsellable units has to be carried by the ones you actually sell.
- How current are the fee tables?
- Every figure carries the official page it came from and the date it was last verified by hand, shown on its own line in the cost breakdown. The build fails outright if any table goes 180 days without re-verification, so the data cannot quietly rot.