Eight numbers cover the health of an Amazon business in a weekly review: net profit, net margin, TACOS, refund rate, Featured Offer (Buy Box) percentage, unit session percentage, days of stock left, and net profit per unit on your top SKUs. Checked in that order, they move from “is the business earning?” to “where exactly did it change?”, which keeps a weekly review to about twenty minutes.
Why a fixed set of numbers?
Seller Central, advertising reports and inventory reports together offer hundreds of metrics. Looking at a different selection each week makes changes hard to spot, because there is nothing consistent to compare against. A fixed set, read in the same order and compared with the previous week and the same week last year, turns the review into a quick check with a clear next step when something moves.
The eight numbers
| # | Metric | Formula | If it moves the wrong way, check |
|---|---|---|---|
| 1 | Net profit | Revenue − COGS − Amazon fees − Advertising − Refund costs − Other expenses | Metrics 2–8 to find the cause |
| 2 | Net margin | Net profit ÷ Revenue | Whether costs grew faster than revenue |
| 3 | TACOS | Ad spend ÷ Total revenue | Campaign budgets, bids, new campaigns |
| 4 | Refund rate | Units refunded ÷ Units sold | Return reasons for the SKUs driving it |
| 5 | Featured Offer (Buy Box) % | Page views where your offer was featured ÷ All page views | Competitor prices, your stock, account health |
| 6 | Unit session % | Units ordered ÷ Sessions | Price, reviews, listing changes, coupons ending |
| 7 | Days of stock left | Available stock ÷ Average daily sales | Reorder timing and inbound shipments |
| 8 | Net profit per unit, top SKUs | Net profit ÷ Units, per SKU | Fee changes, price changes, ad cost per unit |
What does each number tell you?
1. Net profit. The result of everything else. Look at the total first and compare with last week and the same week last year, since seasonality makes week-to-week comparisons misleading in Q4 and around Prime Day.
2. Net margin. Shows whether profit changed because of volume or because of cost. Revenue up and margin down means the growth was bought, usually through advertising or discounts.
3. TACOS. Total advertising cost of sale: ad spend as a share of all revenue, including organic sales. It shows how dependent revenue is on advertising. A rising TACOS with flat revenue means advertising is replacing organic sales rather than adding to them.
4. Refund rate. A refund costs more than the refunded price: Amazon keeps part of the referral fee as an administration fee, the fulfillment fee is not returned, and some returned units cannot be resold. A jump on one SKU often points to a listing, quality or packaging problem.
5. Featured Offer (Buy Box) %. On shared listings, a drop here explains a sales drop before any other metric. Since July 2026 Amazon has been removing the separate seller eligibility step for the Featured Offer, so offers that were excluded before now compete. Watch this number closely on listings with several sellers.
6. Unit session percentage. Amazon’s conversion rate: the share of sessions that ended in an order. If sessions are stable and this falls, something on the listing changed: price, a new negative review, a coupon that ended, a changed image or title.
7. Days of stock left. Stockouts are the most expensive way to lose sales. Compare days of stock left with your lead time for every top SKU. Also watch the low end: below 28 days of historical supply on Amazon’s measures, the low-inventory-level fee can apply.
8. Net profit per unit on your top SKUs. Catches changes the totals hide, such as a fee change after a remeasurement, a price drop from a repricer, or higher ad cost per unit on one product.
Worked example: reading a week
| Metric | This week | Last week |
|---|---|---|
| Revenue | $28,450 | $28,880 |
| Net profit | $4,210 | $4,650 |
| Net margin | 14.8% | 16.1% |
| TACOS | 11.2% | 9.4% |
| Refund rate | 3.1% | 3.0% |
| Featured Offer % | 94% | 95% |
| Unit session % | 12.4% | 12.6% |
| Days of stock left, top SKU | 26 | 41 |
Revenue is almost flat, yet profit fell by $440. TACOS explains nearly all of it: ad spend went from about $2,715 (9.4% of $28,880) to about $3,186 (11.2% of $28,450), an increase of $471. Buy Box share, conversion and refunds barely moved. The action is in the advertising account, not the listings.
Separately, the top SKU is down to 26 days of stock. If its lead time is longer than that, a reorder is already late, and the next weeks’ sales are at risk regardless of advertising.
Best practices
- Use the same eight numbers every week, in the same order.
- Compare with last week and the same week last year.
- Start with profit and work down. Only investigate the metrics that explain the change.
- Write one line of conclusion and one action per review.
- Keep advertising metrics (CPC, CTR, ACOS) for a separate PPC review. The weekly profit review only needs TACOS.
Common mistakes
- Reviewing revenue instead of net profit.
- Reacting to one week’s movement without checking the same week last year.
- Using ACOS instead of TACOS for the business view. ACOS only covers ad-attributed sales.
- Ignoring days of stock left until a stockout shows up in sales.
- Checking account totals only. A problem on one top SKU can hide inside a stable total.
FAQ
What KPIs should Amazon sellers track? At minimum: net profit, net margin, TACOS, refund rate, Featured Offer (Buy Box) percentage, unit session percentage, days of stock left, and net profit per unit on top SKUs.
How often should I review Amazon metrics? Weekly for this set, daily only for stock and Buy Box on critical SKUs during peak periods, and monthly for a full P&L review.
What is a good TACOS on Amazon? It depends on margin and growth stage. The useful test is whether net profit holds as TACOS changes; the trend matters more than a benchmark.
What is unit session percentage? Units ordered divided by sessions, Amazon’s measure of conversion. It is in Business Reports.
Why is profit down when sales are flat? Usually one of three: higher ad spend (TACOS), more refunds, or lower profit per unit from a price or fee change.
Conclusion
A weekly review works when it is short, consistent and ends in an action. Eight numbers, read from profit down, are enough to see whether the business is earning, where a change came from, and whether stock will hold. Anything the eight numbers can’t explain is a signal for a deeper look, not a reason to add more metrics to every week.
sellerboard shows net profit, margin, TACOS, refunds and profit per unit per product on one dashboard, updated throughout the day, alongside stock levels and days of stock left, so most of this review can be read from one screen.
