Chapter 8: BSR, sales and demand
What you'll learn: what Best Sellers Rank tells you, why a "good" rank depends on the category, how ArbiSource's BSR % makes ranks comparable, and how to tell an estimate of sales from a confirmed figure.
What BSR is
Every product that has sold on Amazon.com has a Best Sellers Rank (BSR) in its category. A rank of 1 means it's currently the top seller in that category. The lower the number, the more it's selling.
Three things to know about it:
- It's relative. BSR compares a product's recent sales with every other product in the same category. On its own, it isn't a number of sales.
- It's always moving. A sale usually improves the rank (the number falls); between sales it gradually drifts back up. One snapshot can mislead you, so always look at the history (Chapter 9).
- It's per category. A product can have a main category rank plus one or more subcategory ranks. ArbiSource uses the main category rank.
Why a "good" rank depends on the category
Amazon.com's categories vary enormously in size, and many are far bigger than their equivalents on other Amazon marketplaces. A rank of 100,000 might be a dependable seller in a giant category such as Home & Kitchen, and a slow mover in a small one. That's why no single "buy anything under X" rule works across categories, and why rules of thumb from other marketplaces don't carry over to the US.
BSR %: comparing like with like
ArbiSource handles this with BSR %: the product's rank divided by the number of ranked products in its category, shown as a percentage. A rank of 10,000 in a category with 1,000,000 ranked products is 1%, so the product is in the top 1% of its category, whatever the category's size. The lower the percentage, the better it sells relative to its category.
That makes BSR % the better choice for filters: one setting works in every category. Use BSR % rather than raw BSR in your filters, and leave it fully open at first (4.3).
A maximum BSR (or BSR %) hides slower sellers, which is usually what you want. A minimum BSR hides the fastest sellers, because they have the lowest numbers. Set one by mistake and your best results vanish. It's one of the most common causes of "no results".
Estimated sales and confirmed sales
Amazon doesn't publish how many units a product sells, so you'll see two kinds of sales figure:
| Where it comes from | How to use it | |
|---|---|---|
| Estimated monthly sales | Calculated from the product's rank and how often its BSR drops | A useful guide to demand, but an estimate. Read it as a range, not an exact count |
| Confirmed sales | Amazon's own "bought in past month" figure, where the listing shows one | Stronger evidence of demand. Not every listing has it |
ArbiSource shows both on each result, with confirmed sales for the past 30 days where available. When they broadly agree, you can be more confident.
Your share of the sales
A product selling 200 a month doesn't mean you'll sell 200 a month. Sales are shared among the sellers who win the Buy Box (Chapter 10). A simple way to estimate your slice: divide the monthly sales by the number of competitive FBA sellers, then trim it a little to be safe. That tells you roughly how many units you could sell in a month, and so how many to buy.
a product sells about 120 units a month, and five FBA sellers are priced close to the Buy Box. Your share might be around 20 to 25 a month, so a first order of 6 to 10 units should sell through in a couple of weeks, with room to buy more if it goes well. On a product you're less sure of, that first order is your Test-buy.
Steady demand beats a spike
You're looking for regular sales over months, not one busy week. When you check a product, ask:
- Has it sold steadily over the last 90 to 180 days?
- Is demand seasonal? Toys, gifts, outdoor and back-to-school products can sell far more at certain times of year. Look back 12 months (Chapter 9).
- Is the rank improving, holding steady or getting worse?
ArbiSource's result panel helps here. Its past-performance table shows the BSR (rank and BSR %) and the number of BSR Drops for the last 30, 90, 180 and 365 days, alongside the average Sell Price and Profit / ROI, so you can see at a glance whether a product sells consistently.
The same checks apply to retail arbitrage. Look up a clearance item on your phone (for example in Amazon's Seller app, then its Keepa history), and the rank and price history tell you in seconds whether it belongs in your cart. Practicing on ArbiSource results teaches you what steady demand looks like, which makes you much faster in the aisles.
Checklist
- I know a lower BSR means more sales, and that it only means something within its category
- I won't reuse BSR rules of thumb from other marketplaces
- I use BSR % for filters, and I never set a minimum BSR by accident
- I know the difference between estimated and confirmed sales
- I estimate my share of the sales before deciding how many to buy