First, decide what ACoS you actually want
Before cutting anything, anchor on a number that is true for your product. Your break-even ACoS is the margin left after product cost and Amazon fees, expressed as a percentage of price. Run ads below it and each advertised sale is profitable; run above it and you lose money on every order. A flat "25% is good" rule is meaningless without your margins — a 50%-margin product can profit at a 45% ACoS, while a thin-margin one loses at 25%. Work out yours on the break-even ACoS calculator first.
Cut wasted search terms (the biggest, fastest win)
Most wasted ad spend hides in search terms that get clicks but no orders. Pull your search-term report, sort by spend, and look for terms with meaningful clicks and zero or near-zero conversions. These become negative keywords. Be careful not to negate a term that is also converting elsewhere — and do not act on tiny samples; a term with five clicks and no order is not yet proof of anything. This is exactly the kind of repetitive, every-week task that is easy to skip, which is why it tends to be where the savings sit. See the negative keywords guide for the full method.
Bid each keyword to its real conversion rate
Overbidding is the second big leak. A keyword that converts at 5% cannot justify the same bid as one that converts at 20%. Trim bids on targets whose conversion rate cannot support the cost, and let the winners keep their budget. The goal is not the lowest bid — it is the bid that wins profitable sales. Move in measured steps and watch the effect, rather than slashing bids overnight.
Fix placements and hours
Two quieter drains: placements that get clicks but few orders, and budget spent at hours when shoppers rarely buy. Adjust placement multipliers toward the spots that convert, and use dayparting to pull spend back during low-intent hours based on your real hourly data — not a generic schedule. See dayparting for how this works.
Do it consistently — or automate it
None of these moves is complicated; the hard part is doing all of them, every week, across every campaign, without fatigue. That is the case for automation. AIAdKing lowers ACoS automatically: it harvests negatives, trims losing bids and shifts budget every night on the official Amazon Ads API, logs a reason for each change, and previews everything in shadow mode before it goes live. Whether you do it by hand or automate it, the principles above are the same.
One honest caveat: a lower ACoS is not always the goal. Pushed too far, it starves volume and leaves sales on the table. Optimise for the most profit, not the smallest ACoS.