Most Amazon sellers who lose money on inventory don’t lose it on a bad product. They lose it on a good-looking one they never checked properly — the margin was real, the demand was real, and a shelf full of other sellers’ units was already ahead of theirs.

Once you’ve paid the supplier, the shipping and the prep, and sent the box to an Amazon warehouse, the money is stuck. Units that don’t sell don’t sit for free: they pay storage every month. A few minutes of checking beforehand costs nothing and catches most of it.

You don’t need a subscription for any of it. Here are three checks, in the order that wastes the least time. Each check can end the deal on the spot.

Check 1: Can you actually sell it?

Checking whether you can sell the product is the quickest check and the only one that can make it impossible rather than merely unprofitable, so do it first. Search the product in Seller Central before you spend anything and see what it asks of you.

What to look for

  • Approval. Some brands and categories need Amazon’s approval before you may list them. Finding that out after you’ve bought 200 units is the expensive way.
  • Dangerous goods. Batteries, aerosols, anything flammable or pressurised may need extra classification before the FBA warehouse will accept it.
  • Amazon itself on the listing. If Amazon sells the product, it usually holds the Buy Box. You can be right about every number and still sell almost nothing.

Check 2: Does the margin survive real fees?

Amazon’s own FBA Revenue Calculator is free, and Amazon says a public version works without signing in. Search the product, enter the selling price and what you paid, and it estimates the referral fee, the fulfilment fee and monthly storage, and compares fulfilling through Amazon with doing it yourself.

The FBA Revenue Calculator can’t know two things. It doesn’t know your own costs — prep, shipping the stock to Amazon, returns — so take those off yourself. And it doesn’t know what the price will be when your units arrive. For that you need the price history.

Keepa’s free browser extension draws a price-history chart on the Amazon page. Don’t read it for the price. Read it for the shape: is the price steady, or has it been sliding? Did it just spike? A spike often means stock ran out and the high price won’t last. If your margin only exists at today’s peak, you don’t have a margin.

The bigger paid tools overlap here. SellerAmp has a 14-day free trial, and its plans start at about $20 a month; it has no permanent free tier. Helium 10 has a free plan, but says access to its Chrome extension is limited on it, and its paid plans start at $99 a month billed yearly. They’re worth trying for a focused sourcing week. A trial ends, though, and a limited plan stops where the useful numbers begin.

Check 3: Will it sell, and is the timing right?

This is the check most sellers skip, because it rarely comes free. It comes down to two numbers: how fast the product sells, and how many days the stock already on Amazon will last at that speed. Divide one by the other and you get Days of Cover.

A worked example

Days of Cover = units available on Amazon ÷ estimated units sold per day = 360 ÷ 12 = 30 days

Estimated sales
12 units / day
Units across all sellers
360 units
Your order reaches Amazon in
25 days

Thirty days of cover and a 25-day lead time means you arrive as the shelf is running empty. If your units took 90 days to get there, the shelf has most likely been refilled long before you.

Tight cover with steady demand is the good case. Sellers drop out of stock, competition thins, and prices tend to firm. Plenty of cover is the bad one. Your units queue behind everyone else’s, pay storage the whole time, and the price is more likely to slide as sellers compete to move what they hold.

How we read it

Ripe

Ripe — opportunity

Profit and inventory line up: the stock on Amazon is running down and the margin holds. Worth acting on.

Ripening

Ripening — watch

Interesting, but not there yet. Keep an eye on it as inventory and prices move.

Rotten

Rotten — pass for now

The numbers don’t support the buy today. Walk away, or wait.

You can do this by hand if you can see every seller’s stock. Or you can let us do the arithmetic.

What the free page doesn’t show is the individual sellers and how many units each holds. Those sit behind an account. It’s also a snapshot: Days of Cover keeps moving, and a product that reads Ripening today can be ripe next week. If you want to be told when, put it on a list and let it be watched.

The 15-minute routine

  • Seller Central: does it need approval, is it hazmat, is Amazon selling it?
  • FBA Revenue Calculator: put in your real price and your real costs. Is the profit still worth it?
  • Price chart: is the price steady, or only high right now?
  • ASIN analysis: how many days of cover are left, and how does that compare with your lead time?

If any one of them fails, you’ve just kept the price of a pallet in your pocket.

The cheapest unit to lose money on is the one you never bought.