PPC · Profitability
True ACoS vs ACoS: the number that's quietly draining your Amazon profit
Most Amazon sellers steer their advertising by ACoS — Advertising Cost of Sales. It's the default column in every ad console, so it feels like the number that matters. The problem: ACoS can look perfectly healthy while you lose money on every single unit you sell. This guide explains why, and how to switch to the metrics that actually protect your margin.
What ACoS actually measures
ACoS is simple: ad spend divided by ad-attributed sales.
ACoS = Ad Spend ÷ Ad Sales × 100
If you spent ₹1,000 on ads and those ads drove ₹5,000 in sales, your ACoS is 20%. Lower looks better. But notice what's missing: ACoS knows nothing about what the product costs you. It compares spend to revenue, not to profit. A 20% ACoS tells you nothing about whether that sale made or lost money.
Why a "good" ACoS can still lose money
Take a product selling at ₹1,000. Before a rupee of advertising, Amazon and fulfilment already take their share:
| Line item | Amount |
|---|---|
| Selling price | ₹1,000 |
| Referral fee (~15%) | −₹150 |
| FBA / fulfilment fee | −₹90 |
| Product cost (COGS) | −₹450 |
| Returns & refunds (allocated) | −₹70 |
| Margin before ads | ₹240 |
You have ₹240 of margin to work with. That means your break-even ACoS is 24% — spend more than ₹240 in ads per ₹1,000 of sales and the unit is underwater. So a campaign running at a "healthy-looking" 20% ACoS is barely profitable, and one at 30% ACoS — which many sellers happily tolerate — is losing money on every order. ACoS never told you, because it never saw your costs.
The three numbers you actually need
1. Break-even ACoS (a.k.a. true ACoS)
Your total margin percentage after all fees, COGS and returns — the ACoS at which a product stops being profitable.
Break-even ACoS = Margin after all costs ÷ Selling price × 100
Every product has its own break-even ACoS. A high-margin private-label item might break even at 40%; a thin-margin reseller SKU at 12%. Optimising every campaign to the same target ACoS ignores this and quietly scales your worst products.
2. TACoS (Total Advertising Cost of Sales)
Ad spend divided by total sales — organic plus paid.
TACoS = Ad Spend ÷ Total Sales × 100
TACoS shows whether advertising is buying durable organic momentum or just renting clicks. Falling TACoS while sales grow is the healthiest signal in Amazon advertising: your ads are lifting organic rank, so each sale needs less paid support over time.
3. Contribution margin per SKU
The rupee figure that survives after every cost and ad spend. This is the number that actually lands in your bank account, and the one you should be scaling — not a ratio.
How to act on it
- Set target ACoS per product, from its break-even — not one global number. Aim comfortably below each SKU's break-even ACoS, leaving room for profit.
- Cut spend on SKUs running above break-even — these are the campaigns losing money while their ACoS looks "fine".
- Push budget toward high-contribution-margin SKUs, even at a higher ACoS, because the rupee profit is larger.
- Watch TACoS monthly. If it's rising while organic sales stall, your ads aren't building rank — they're propping up demand that vanishes when you pause.
Why most sellers never do this
Not because it's complicated — because the data lives in three places. Ad spend is in the Ads console. Fees and returns are in Seller Central settlements. COGS is in a spreadsheet. Stitching them together per SKU, every week, by hand, is the job nobody finishes. So sellers fall back on the one number that's already on screen: ACoS.
This is exactly the gap BI Adlytics closes. It reconciles your settlements — referral fees, FBA fees, storage, returns and refunds — against real ad spend, per product and per day, and shows contribution margin and break-even ACoS next to each campaign. You see which "healthy" campaigns are actually losing money, and you can push the fix back to Amazon as a bulk change in one step.