Why does ACOS usually fall the wrong way?
Because the fastest way to improve a ratio is to shrink the top of it. Cut bids across the board and ACOS improves within days — along with impressions, clicks, orders, and eventually organic rank.
That is why ACOS is a diagnostic, not a goal. When the numbers conflict, the order is profit first, then revenue, then ACOS. An agency showing you a greener ACOS chart while profit falls has not done its job.
What is the first thing to fix?
Spend that was never going to convert. It costs you nothing to remove, because it was not producing sales.
- Open the search-term report over a window long enough to be meaningful.
- Sort by spend, then filter to terms with zero orders.
- Ignore anything without enough clicks to be a signal.
- What remains is your monthly leak. Add those terms as negative exact.
This is the one move that lowers ACOS without touching a single sale. Everything after it involves a trade-off.
What do you do after the obvious waste is gone?
Cutting waste is half the job. The other half is moving budget toward what already works:
- Harvest. Terms converting reliably in auto or broad campaigns get promoted to exact match in your performance campaign, where you can bid on them deliberately.
- Negate wrong intent. Terms that occasionally convert but describe a different product should still go. They dilute relevance and cost you on the majority of clicks.
- Adjust bids against break-even, not a target. Work out the break-even ACOS for that product first — our calculator does it in a few seconds — then judge each campaign against its own number.
- Check placements. Top-of-search often carries a modifier that made sense once and has not been reviewed since.
What should you check before touching anything?
Two things, every time, and they save more money than any bid rule:
- Stock. Never optimise toward an ASIN that is about to run out. You will pay to teach the algorithm a lesson you then have to unteach when it returns.
- Account health and listing status. A suppressed listing or a broken buy box makes every PPC decision below it academic.
What quietly makes ACOS worse?
The common self-inflicted ones:
- Reacting to insignificant data. Three clicks is not a signal.
- Over-negating. It feels productive and it slowly strangles discovery, which is where next quarter's converting terms come from.
- Changing many things at once. You learn nothing, and you cannot attribute the result to anything.
- Changing bids without logging why. When performance moves in week six, the log is the only way to know which change did it.
- Buying traffic you already own. Heavy branded spend can look efficient while mostly harvesting sales you would have had anyway.
What this will not fix
ACOS work cannot rescue a product whose economics do not work. If the margin is too thin to carry any advertising, no bid strategy fixes that — the problem is price, cost, or fees, and it needs solving before ads are worth optimising.
It also will not fix a listing that does not convert. If clicks are arriving and orders are not, the ads are working and the page is not.
Where to go next
Questions people actually ask
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