ROI Calculator

ROI is the most misused number in Amazon. People quote it on revenue ("I got a 3x return!") when what they mean is they sold three times what they spent — which sounds great until you realize it ignores the months the cash was stuck in a container.

This calculator measures ROI the way a cash-constrained seller should: profit divided by the money you actually tied up in inventory, with the sell-through time made explicit.

The inputs

• Units purchased and cost per unit (landed) — landed means including freight and duty, not the ex-factory price. The ex-factory number makes ROI look better than it is.
• Net profit per unit — use the Net Profit Calculator so this already has fees and PPC taken out.
• Days to sell through — how long until the batch is gone. This is the lever most people ignore.

Why time matters

Two products can show the same 50% ROI per cycle. One sells out in 30 days, the other in 180. The first one lets you reload six times a year; the second, twice. Same per-batch return, but the fast one earns three times the cash annually on the same inventory budget. When you're capital-limited — and almost everyone is at some point — velocity beats margin.

The annualized figure this tool shows is an "if you could repeat it" number. It assumes you always have product ready to ship and never sit on empty shelves or wait six weeks for a container. Real life is messier, so treat annualized ROI as the ceiling, not the promise.

What a good number looks like

There's no single right answer, but I've seen healthy businesses run 25–50% ROI per 60–90 day cycle. Below that, your cash is working harder in a savings account with none of the risk. Above it, check your inputs — often the sell-through time is too optimistic or the PPC cost is understated.

The point of this calculator isn't to hit a target. It's to compare two product ideas on equal footing, including how long the money is locked up, before you write the purchase order.