Break-Even ACOS Calculator

Break-even ACOS is the single most useful number in Amazon PPC, and most sellers never compute it. It's your profit margin before ads. That's the whole formula. If your product keeps 25% of the sale after COGS, fees, and everything else, then 25% is your break-even ACOS. Bid past it and you bleed on every ad-attributed sale.

I wasted a full quarter once because I never wrote this number down. My auto campaigns were "performing" — lots of orders — and I kept raising bids to win more placements. What I was actually doing was paying more per click than my margin could absorb. The sales looked great in Seller Central. The bank account disagreed.

Why it's your margin

An ad-attributed sale still has the same COGS, referral fee, and FBA fee as an organic one. The only thing the ad adds is the click cost. So the most you can spend acquiring that sale, as a share of the sale, is exactly your margin. Spend less and you profit. Spend more and you're buying revenue at a loss.

Reading the table

The table shows max ACOS at a few common margins:

• 10% margin — your ads can't exceed 10% ACOS or you lose money on those orders.
• 15% margin — a little room, but bids still have to stay tight.
• 20% margin — comfortable enough to test aggressive placements.

If your real margin is thinner than you thought, your break-even ACOS drops with it. That's why guessing the margin is dangerous — a number pulled from memory is usually too high, and you bid like you're richer than you are.

TACOS still matters

Break-even ACOS is about ad-attributed sales. If your ads also lift organic sales (they usually do, especially on branded terms), your true break-even is higher because the ad is doing double duty. But don't bank on that to justify a bad ACOS. Measure it, don't assume it.

Set your bids below this line. Everything above it is you paying customers to take product. Run the Max CPC Bid Calculator next to turn this number into an actual bid you can type into the campaign.