For a long time, I was completely focused on keeping ACoS as low as possible. It
By Michael Erickson Facchin · May 31, 2026 · Curated by George's Blog
For a long time, I was completely focused on keeping ACoS as low as possible.
It’s what most of us are taught to do with Amazon PPC.
But blindly forcing ACoS down without understanding your actual margins is a trap. Here is what that looked like for one of our brands before we finally mapped out our numbers.
Before:
- We kept our ACoS strictly under 15% because we thought "lower is always better."
- We paused or drastically lowered bids on high-volume keywords the second they got "expensive."
The reality: Our ad spend looked incredibly efficient on paper, but our overall sales volume was terrible. By artificially starving our campaigns to hit an arbitrary low ACoS, we were leaving massive amounts of money on the table.
The Pivot:
- We stopped guessing and looked at the math. We calculated that our Break-Even ACOS was actually 55%.
- Instead of aiming for "as low as possible," we worked backward. We wanted a solid Target Profit Margin of 15%.
Math made it simple: 55% (Break-Even) - 15% (Profit Margin) = 40% Target ACOS.
After:
- We gave our campaigns room to breathe, allowing ACoS to rise to our target of 40%.
- We bid aggressively on top-converting keywords to win Top of Search placements.
The reality: Our sales velocity skyrocketed. Because we were spending up to a mathematically proven Target ACoS, we consistently secured our 15% profit margin, but at a much higher volume. Total net dollars in the bank went way up.
Lesson learned: Optimizing for an arbitrarily low ACoS often strangles your growth. Knowing your exact Break-Even ACoS gives you the permission and the confidence to spend profitably.
Has anyone else made the shift from chasing "low ACoS" to actually spending based on Break-Even and Target margins?