How to calculate maximum product cost
Conceptually the maximum you can pay a supplier is what is left after everything else is taken out of the sale price:
Maximum product cost = selling price − Amazon fees − shipping − duty and import fees − advertising − other costs − target profit
That formula is right about what belongs in the calculation. It is wrong about the arithmetic — and the error is not small.
Why the simple subtraction gives the wrong number
The formula assumes every cost is a fixed amount you can subtract once. Several are not: they change depending on the price and on each other.
- Referral fee thresholds. In Clothing and Accessories, a $15.00 sale is charged 5% and a $15.01 sale is charged 10% — on the whole price, not the extra cent. Cross that line and your fee jumps by $0.75 while your revenue rises by $0.01.
- Fulfilment fee price bands. Amazon charges different fulfilment rates below $10, between $10 and $50, and above $50. The same product costs more to ship the moment you price it a cent over the band.
- The Merchandise Processing Fee floor and cap. MPF is 0.3464% of customs value, but never less than $33.58 or more than $651.50 per entry. It has to be worked out for the whole shipment and then divided by units — divide first and every unit hits the floor.
- Advertising as a share of revenue. If you budget ads as a percentage, raising the price raises the ad spend too, so part of the increase is eaten before it reaches profit.
How this calculator does it instead
Rather than inverting the formula, this tool runs the full profit calculation repeatedly and narrows in on the answer — a binary search on the actual rate tables, settled to the cent.
That is slower than a subtraction and completely worth it: the answer comes from the same engine that produces the cost breakdown, so the two can never disagree. There is no second, simplified copy of the fee rules to drift out of date.
It also means the tool can tell you something a formula cannot: where the pricing cliffs are. Those are the points where raising your price by one cent makes you less money, because the whole price moves into a higher fee band.
Break-even price, minimum selling price and maximum CPC are one question asked three ways
Set the target to zero and the minimum selling price this tool returns is your break-even price. Set it to the margin you actually want, and the same solver gives you the price that reaches it. Nothing about the calculation changes — only the number you are aiming at.
The advertising side works the same way. Maximum ad spend per unit is the budget at which the target is exactly met. Divide that budget by the clicks it takes to make one sale — twenty of them at a 5% conversion rate — and you have the maximum CPC: the most a single click can cost before the target slips away.
So a break-even calculator, a minimum selling price calculator and a maximum CPC calculator are three names for boundaries of the same equation. This one gives you all of them from a single set of inputs, and finds every boundary by running the real fee tables rather than by rearranging a simplified formula.
What costs are included
Every line says which kind of figure it is: an official rate from a published table, something you supplied, or an estimate shown as a range. The results page also lists the cost blocks it did not include, and why — a zero because you left an input blank looks exactly like a zero because the cost does not apply, unless someone tells you which it was.
- Product cost, domestic freight to the port, packaging and prep
- First-leg international freight
- Import duty, additional tariffs, Merchandise Processing Fee, Harbor Maintenance Fee
- Amazon referral fee, FBA fulfilment fee, monthly storage, inbound placement, Overmax handling
- Returns processing, removal or disposal of dead stock
- Advertising, FX spread on repatriating revenue
How much should I pay my supplier?
Treat the number as a ceiling, not a target. It is the price at which you exactly hit your goal and not a cent more, with every other input held where you set it.
The volatile parts of the calculation are advertising and returns — the two things you control least in the first months of a listing. If you want the target to survive a bad quarter, use the conservative scenario, which takes the unfavourable end of every estimate, and buy below the figure it gives you.
Common questions
- Does this include import duty?
- Yes, if you tick “Sourced overseas”. It computes customs value on the FOB basis the United States uses — duty is assessed on the goods, not on the freight — then adds the Merchandise Processing Fee with its per-entry floor and cap, and the Harbor Maintenance Fee on ocean shipments only. The duty rate itself is one you supply: this tool does not look up HTS codes yet, and it says so on the line rather than implying the rate came from us.
- Is the maximum product cost before or after shipping?
- It is the unit price you pay your supplier, before freight. Domestic freight to the port, packaging and prep, and first-leg international freight are separate inputs, and they are already accounted for in the limit you get back.
- Why is my maximum lower here than in another calculator?
- Usually because the other one leaves out import duty, MPF and HMF entirely, or because it assesses duty on the full landed cost including freight. The United States assesses duty on the goods alone, so including freight in the base overstates duty — which flatters your maximum product cost rather than protecting it.
- What if no supplier price reaches my target?
- Then the tool says so instead of showing a number. It means the target cannot be reached by buying cheaper alone — even at a cost of one cent — and you would need a higher price, lower advertising, or a different product. The decision summary shows how far each of those levers would have to move.
- Do the three limits apply at the same time?
- No, and this is the most common way to misread the result. Each limit is calculated with every other input held exactly where you set it. They are three separate boundaries — any one of them on its own reaches the target. Pushing all three to their limits at once overshoots and loses money.