Calculator
Margin & break-even calculator
Your numbers, not ours. Nothing is stored and nothing leaves your browser — this page has no server side at all.
Your numbers
Result
How each line is calculated
| Output | Formula |
|---|---|
| Referral fee | price × referral rate |
| Return cost | (fulfillment + COGS + inbound) × return rate — a returned unit costs you the fulfillment and often the unit |
| Ad cost | price × TACOS |
| Total cost | COGS + inbound + referral + fulfillment + storage + returns + ads |
| Net profit | price − total cost |
| Net margin | net profit ÷ price |
| ROI | net profit ÷ (COGS + inbound) |
| Break-even price | fixed costs ÷ (1 − referral rate − TACOS) |
| Max ACOS | profit before ads ÷ price |
The return-cost line is the one most calculators leave out. A returned unit is not simply a reversed sale: you generally lose the outbound fulfillment, and depending on condition you may lose the unit. Treating returns as free is how a 20% margin turns out to be 12%.
A worked example
A standard-size product selling at $29.99, sourced at $6.20 a unit landed, with a 15% referral rate. Substitute your own figures — the point is the shape of the result, not these numbers.
| Line | Amount | Where the figure comes from |
|---|---|---|
| Selling price | $29.99 | Your listing |
| Cost of goods, landed | −$6.20 | Supplier invoice plus freight, duty and prep per unit |
| Inbound to the fulfilment centre | −$0.55 | Your carrier invoice divided by units in the shipment |
| Referral fee at 15% | −$4.50 | Category referral rate |
| Fulfilment fee | −$5.60 | Fee Preview report, at your size tier and price band |
| Storage, allocated per unit | −$0.18 | Monthly storage bill divided by units sold that month |
| Returns at a 6% rate | −$0.74 | Return rate from your own returns report |
| Advertising at 9% TACOS | −$2.70 | Ad spend divided by total sales, not ad-attributed sales |
| Net profit per unit | $9.52 | |
| Net margin | 31.7% | |
| Maximum ACOS before this stops paying | ~40.7% |
Two lines in that table are the ones sellers most often get wrong. Storage is allocated per unit sold rather than per unit held, which understates it badly on slow movers. And TACOS rather than ACOS is the correct input, because advertising is paid out of total revenue and not only out of the sales it is credited with.
What this calculator assumes
Every calculator carries assumptions. Stating them is the difference between a tool and a guess with a rounded corner.
- One unit, one sale. Multipacks and bundles change the fulfilment fee and the size tier — enter the packed configuration you actually ship.
- A returned unit costs you the outbound fulfilment and, depending on condition, the unit itself. That is the default here. Where returns are resold as new, your real return cost is lower.
- Storage is a per-unit allocation. It is not a per-unit charge in reality; it is a monthly bill on volume held. Allocating it per unit sold is the practical approximation.
- No peak-season adjustment. Q4 storage and holiday fulfilment surcharges are not modelled — run peak separately with the higher figures.
- Referral fee is applied to the selling price alone. Some marketplaces charge on price plus shipping; on those, enter an effective rate rather than the headline one.
- No currency conversion. If you bank in a different currency from the marketplace, your real proceeds are lower by the conversion cost.
Reading the result honestly
- Below 10% net — one fee change or one bad month of advertising erases it. Since selling price became an input to the US fulfillment fee in January 2026, even a repricing decision can move your costs.
- 10–20% net — workable, but there is no room for error in sourcing or ad efficiency.
- Above 20% net — enough buffer to absorb a fee increase, a return spike, or a competitor undercutting you for a quarter.
The max ACOS number is the more useful one for most people. It tells you the point at which advertising stops being growth and starts being a subsidy. If your current TACOS is close to it, you are running a business that exists to feed the ad platform.
The figures this calculator needs, explained
Three of the inputs above are the ones people estimate rather than measure, and each has a guide behind it.
- Landed cost — what a unit really costs by the time it is sellable, which is the figure the cost-of-goods box wants.
- The 2026 fee changes — why the fulfilment fee has to come from your own Fee Preview report rather than a published average.
- Price bands — since January 2026 the selling price is an input to the fulfilment fee, so changing the price in this calculator changes a cost too.
- Returns — where the return rate comes from and what a return actually costs beyond the lost sale.
- Storage — the four separate charges the storage box is standing in for.
Frequently asked
Where do I get the fulfillment fee number?
Your Fee and Economics Preview report in Seller Central, or the Revenue Calculator for a specific ASIN. Do not estimate it — since January 2026 the US fulfillment fee depends on selling price as well as size and weight.
Is my data sent anywhere?
No. This page is a static file with no server side. The calculation runs in your browser and nothing is stored or transmitted.
Why is my margin lower here than in other calculators?
Most likely the return cost and ad spend lines. Many calculators omit both, which produces a flattering number that does not match your settlement report.
What return rate should I use?
Your own, from your returns report. Category averages vary enormously — apparel behaves nothing like consumables — so a generic figure will mislead you.