At what ACOS do you start losing money?

Enter list price, tax rate, royalty rate and printing cost. The calculator tells you, for every book, the point at which an Amazon Ads campaign costs more than it brings in. You do not need any campaign data — it cancels out of the equation.

How the maths works

Four numbers are enough, because everything else follows from them. First the price without tax, since KDP pays the royalty on the net price:

Net price       = list price ÷ (1 + tax rate)
Royalty         = net price × royalty rate − printing cost
Break-even ACOS = royalty ÷ list price

Substituted into one another, the royalty drops out:

Break-even ACOS = royalty rate ÷ (1 + tax) − printing cost ÷ list price

Neither ad budget nor units sold appear in it. That is why the limit is fixed as soon as the book is.

A worked example

A paperback at $12.99, no sales tax in the list price, 60 % royalty at KDP, $2.50 printing cost per copy:

Add 7 % VAT, as German book prices carry, and the same book breaks even at 36.8 % instead. The tax rate alone moves your limit by four percentage points. Why there is no such thing as a good ACOS .

Break-even is a ceiling, not a target. What you should actually aim for is worked out by the target ACOS calculator .

Common questions

What is the break-even ACOS?

The share of revenue you may spend on advertising before you start losing money. Below it something is left over. Above it the advertising costs more than the book brings in.

Do I need numbers from my campaigns?

No. The break-even ACOS depends on the book alone: list price, tax rate, royalty rate and printing cost. Ad spend and units sold cancel out of the equation.

Why is the royalty based on the net price but the ACOS on the gross price?

Because the two numbers come from different places. KDP pays the royalty on the price excluding tax, while Amazon Ads reports revenue at the full list price. Mixing the two makes every campaign look better than it is.

Is my data stored anywhere?

By default it stays in your browser. Only when you create a link does the server store your list under a random ID. There is no account, no sign-up and no email address.

What does the calculator cost?

Nothing. There is no sign-up, no trial and no paid tier.