product research
One of the most expensive mistakes in Amazon FBA is placing a big order for a product without knowing if it actually sells. The margin can look perfect in the calculator, but if there's no real demand, that margin never materializes. Before putting money down, it's worth researching demand with what's already public.
On many listings, Amazon shows a note right below the price like "X+ bought in past month". It's real data, published by Amazon, not a third-party estimate — and by far the best free reference available today. If the competitor's listing shows it, you already have a real monthly sales floor to work with.
Not every listing shows that note. When it's missing, there are indirect signals that help build an idea (imperfect, but useful):
It's common to see calculators that promise to convert Amazon's ranking (BSR) directly into "X sales per month." Be cautious with those numbers: Amazon doesn't publish an official formula, and the paid tools that do this conversion (Jungle Scout, Helium10, etc.) use proprietary models, calibrated on private data, with a real margin of error. They're useful as an additional reference, but shouldn't be the only basis for a large purchase decision.
Once you have an estimate of your competitor's demand (even a rough one), the next step is to cross it with your own margin: if the competitor sells 300 units a month at a given price, how much would you make capturing 10% of that demand at your own price? That's the calculation that actually tells you whether the order is worth it.
Enter the competitor's price and estimated sales, and the calculator projects how much you'd make capturing part of that demand — cross-checked against your real margin, not in the abstract.
Open the calculator →