Tools
Calculators, not another article
Everything here runs in your browser on numbers you supply. Nothing is stored, nothing is sent anywhere, and none of it asks for an email.
Margin & break-even calculator
Enter your own price, cost, fees and ad spend. Returns net profit per unit, net margin, break-even price and the ACOS ceiling you can afford.
The single number that decides whether a product is worth sourcing.
OpenTariff stack estimator
Enter your customs value and the duty layers for your HTS code. Returns the effective rate, total and per-unit duty, and the 10% marking-duty exposure if goods arrive unmarked.
Only one layer is printed in the schedule - the bill is all four, stacked on the same entry.
OpenPPC launch budget calculator
Enter margin, CPC and conversion rate. Returns your break-even ACOS, cost per ad order, a daily budget built backwards from target orders, and how many weeks your cash funds.
Launch ads usually lose money per order — the question is how much per week, and for how long you can pay it.
OpenCash flow & reorder planner
Models the gap between paying a supplier and being paid by the marketplace, and tells you whether you can fund the reorder.
Undercapitalisation is usually a timing problem, not a budget problem.
OpenDimensional weight checker
Compares actual weight against volumetric weight using the standard divisor, and shows how close you are to the next round-up.
Billable weight is what you pay for, and it is often not the weight on the scale.
OpenModel fit check
Fifteen questions on capital, contacts, time and downside tolerance. Scores five selling models against your actual situation.
Most people pick a model before checking whether it fits them.
OpenFree spreadsheet templates
A working FBA reimbursement and claim tracker in Excel. Direct download.
Claims that nobody chases are the most common quiet loss.
OpenWhy these and not a fee calculator
There are already a dozen Amazon fee calculators, several run by companies with live API access to the fee tables. We are not going to build a worse one and hardcode numbers that go stale.
What is missing is tooling for the decisions around the fee: whether the margin survives it, whether your cash comes back in time to reorder, and whether your packaging is quietly pushing you into a higher billable weight. Those depend on your numbers, not on a table we would have to maintain.
For exact per-ASIN fees, use Amazon's own Revenue Calculator and the Fee and Economics Preview report. Those are authoritative. Nothing on this site is.