What is breakeven ACoS for a KDP book?

The ACoS at which ad spend exactly equals your per-sale margin: (royalty − other costs) ÷ list price. A $9.99 book earning $3.10 royalty breaks even at 31% ACoS — above that, each advertised sale loses money.

Why can a low ACoS still lose money?

Because ACoS compares spend to revenue, not to royalty. Amazon keeps printing costs and its share, so a 25% ACoS on a book with a 20% royalty margin is unprofitable even though 25% sounds healthy.

Should I use list price or royalty?

Both, in different places: ACoS is defined against sales revenue (list price), but profitability comes from your royalty. That is why this calculator asks for each separately instead of assuming one universal KDP margin.

How do I set a target ACoS?

Decide the profit you want per advertised sale, subtract it from your margin, and divide by list price: (royalty − costs − desired profit) ÷ price. Campaigns above the target but below breakeven still make some money, just less than intended.

KDP Breakeven ACoS Calculator

Find the ACoS where your Amazon Ads stop making money — from your own royalty, not an assumed margin — before you fund a campaign.

List price ($)

Royalty per sale ($)

From your KDP dashboard: 60% of list price minus printing cost (paperback).

Other costs per sale ($, optional)

Desired profit per sale ($, optional)

Breakeven ACoS

31.0%

Target ACoS (with profit)

21.0%

Max ad spend per sale

$3.10

Profit per advertised sale at different ACoS levels
ACoS	Ad spend / sale	Profit / sale
5.0%	$0.50	$2.60
10.0%	$1.00	$2.10
15.0%	$1.50	$1.60
20.0%	$2.00	$1.10
25.0%	$2.50	$0.60
30.0%	$3.00	$0.10
40.0%	$4.00	$-0.90 (loss)

Formula: breakeven ACoS = (royalty − other costs) ÷ list price. This is per-sale arithmetic from numbers you supply — it does not predict sales volume, conversion rates or campaign performance, and it is not advertising advice. Calculations run in your browser; nothing is stored.

How the kdp breakeven acos calculator works

Amazon defines ACoS as ad spend divided by attributed sales revenue. But revenue is not what you keep — your royalty is. The breakeven point is where ad spend per sale equals your per-sale margin (royalty minus any other variable costs). Divide that margin by list price and you get the ACoS you must stay under. Add a desired profit per sale and the same formula gives your target ACoS.

Worked example: $9.99 coloring book

List price $9.99, royalty $3.10, no other costs: breakeven ACoS = 3.10 ÷ 9.99 = 31.0%, and the most you can pay for ads per sale is $3.10. Wanting $1.00 profit per sale drops the target to 2.10 ÷ 9.99 = 21.0%. A campaign running at 25% ACoS earns money, but less than the $1.00 goal.

Common mistakes

Judging campaigns by revenue ACoS alone. A "good-looking" 30% ACoS is a loss if your margin is 25% of price.
Assuming a universal KDP margin. Printing cost varies with page count, trim and ink — use your book's actual royalty from the KDP dashboard.
Forgetting other per-sale costs. Design outsourcing amortization or licensing fees shrink the real margin.
Treating breakeven as the goal. Breakeven ads build rank, not income — decide deliberately which one you are buying.

Frequently asked questions

What is breakeven ACoS for a KDP book?: The ACoS at which ad spend exactly equals your per-sale margin: (royalty − other costs) ÷ list price. A $9.99 book earning $3.10 royalty breaks even at 31% ACoS — above that, each advertised sale loses money.
Why can a low ACoS still lose money?: Because ACoS compares spend to revenue, not to royalty. Amazon keeps printing costs and its share, so a 25% ACoS on a book with a 20% royalty margin is unprofitable even though 25% sounds healthy.
Should I use list price or royalty?: Both, in different places: ACoS is defined against sales revenue (list price), but profitability comes from your royalty. That is why this calculator asks for each separately instead of assuming one universal KDP margin.
How do I set a target ACoS?: Decide the profit you want per advertised sale, subtract it from your margin, and divide by list price: (royalty − costs − desired profit) ÷ price. Campaigns above the target but below breakeven still make some money, just less than intended.