If you only track one number on your Amazon account, you’re probably tracking the wrong one. Most sellers obsess over ACoS — but ACoS alone can hide whether your business is actually growing. Here’s how to read both metrics like an operator.
What ACoS actually tells you
ACoS (Advertising Cost of Sales) = ad spend ÷ ad-attributed sales.
If you spent $200 on ads and those ads drove $1,000 in sales, your ACoS is 20%. It measures one thing well: how efficient your advertising is. Lower ACoS means each ad dollar is working harder.
The trap: ACoS only looks at sales your ads directly generated. You can get a beautiful 12% ACoS by only bidding on your own branded terms — while your total sales flatline. Efficient, but not growing.
What TACoS tells you
TACoS (Total Advertising Cost of Sales) = ad spend ÷ total sales (ads + organic).
This is the number that reflects business health. Because it includes organic sales, TACoS shows how your advertising affects your whole account, not just the ad-attributed slice.
- TACoS falling while sales grow → your ads are driving organic rank, and the flywheel is working. This is the goal.
- TACoS rising while sales are flat → you’re leaning on ads to prop up sales that aren’t compounding.
- TACoS very low but sales stagnant → you may be under-investing and leaving growth on the table.
How to use them together
ACoS is your steering wheel; TACoS is your destination. In practice:
- Use ACoS to manage campaign- and keyword-level efficiency day to day.
- Use TACoS as the monthly scorecard for whether advertising is actually building the business.
- Never cut ACoS so aggressively that total sales (and TACoS context) suffer — a “win” on efficiency that shrinks the business is a loss.
The agencies that only report ACoS are showing you the flattering number. The ones worth keeping report both — and tie them to profit.
Want to see your real TACoS and what it says about your account? Request a free audit.