Amazon PPC glossary
ACOS (Advertising Cost of Sales)
ACOS tells you how much of your ad-driven sales went back to Amazon as ad cost. A lower number means each ad dollar is earning more. Whether a number is good depends on your profit margin, so always compare it to your break-even ACOS.
Example
You spend $20 on ads and those ads bring in $80 in sales. $20 divided by $80 is 0.25, so your ACOS is 25%.
Where it matters most: Book 1, The Amazon PPC Clarity Guide, in the chapter “Bid Optimization.”
Work out your own break-even ACOS with the free calculator
Go deeper
The glossary gives you the one-line answer. The Amazon PPC Clarity Guide explains why it matters and what to do about it.