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Advertising Break-Even Calculator

Find the highest cost per click and ACOS your book can afford, and the maximum CPC that still keeps a target profit on each sale.

Your Inputs

$
$

Not sure? Use the KDP Royalty Calculator.

%

Orders divided by clicks.

$

Your average cost per click.

$

Profit you want to keep from each ad-driven sale.

Your Results

Warning: Profitable, above target

Your current CPC is below break-even, so ads still make money, but above your maximum sustainable CPC, so you earn less than your target per sale.

Break-even CPC
$0.50
Highest average CPC with no loss
Break-even ACOS
33.3%
Royalty ÷ selling price
Max sustainable CPC
$0.40
Keeps your target profit per sale
Profit per click at current CPC
$0.10
Clicks per sale
10
Ad cost per sale at current CPC
$4.00
Compare with your $4.99 royalty

About the Advertising Break-Even Calculator

Every book has a ceiling on what it can pay for advertising, set by two numbers: the royalty you earn per sale and the share of clicks that buy. This calculator turns those into the limits you can actually use when bidding.

Break-even CPC is the average cost per click at which ads neither make nor lose money. Break-even ACOS is the same limit expressed the way Amazon reports it: your royalty divided by your selling price. Max sustainable CPC goes one step further and keeps a target profit per sale, so you are not just breaking even. The calculator then checks your current CPC against these limits, showing profit per click, clicks per sale and the ad cost of each sale.

Use it before setting bids on a new campaign, after a price change, or whenever your conversion rate shifts. Paperback authors in particular benefit, because printing costs leave less royalty per sale and therefore less room for ad costs. Pair it with the KDP Ad Profit Calculator to model a whole budget.

How It Works

Break-even CPC is your royalty per sale multiplied by your conversion rate. Max sustainable CPC uses royalty minus your target profit per sale instead.

Break-even ACOS is your royalty per sale divided by your selling price.

At your current CPC, profit per click is break-even CPC minus current CPC. Clicks per sale is 1 divided by the conversion rate, and the ad cost per sale is current CPC divided by conversion rate.

The status compares your current CPC with both limits: profitable within target, profitable but above target, at break-even, or unprofitable.

Formula

Break-even CPC
Break-even CPC = Royalty per sale × Conversion rate
Max sustainable CPC
Max CPC = (Royalty per sale − Target profit per sale) × Conversion rate
Break-even ACOS
Break-even ACOS = Royalty per sale ÷ Selling price
Ad cost per sale
Cost per sale = Current CPC ÷ Conversion rate

Example

$14.99 paperback, $4.99 royalty, 10% conversion, $0.40 current CPC, $1.00 target profit

  1. Break-even CPC: $4.99 × 10% = $0.499.
  2. Break-even ACOS: $4.99 ÷ $14.99 = 33.3%.
  3. Max sustainable CPC: ($4.99 − $1.00) × 10% = $0.399.
  4. Profit per click at $0.40: $0.499 − $0.40 = $0.099.
  5. Clicks per sale: 1 ÷ 10% = 10. Ad cost per sale: $0.40 ÷ 10% = $4.00.

The ads are profitable, earning about $0.10 per click, but $0.40 is just above the $0.399 max sustainable CPC, so each sale keeps about $0.99 rather than the full $1.00 target.

Important Notes

  • All limits are averages. Individual keywords can sit above or below them.
  • Conversion rate needs enough data, ideally several hundred clicks, to give stable limits.
  • Kindle Unlimited page reads and series read-through are not included and can justify higher bids.
  • Use the royalty for the format being advertised. Mixed-format sales need a blended royalty and price.
  • Taxes and currency conversion are not included.

Frequently Asked Questions

What is the difference between break-even CPC and max sustainable CPC?

Break-even CPC is the point of zero profit. Max sustainable CPC is lower, because it keeps your target profit per sale. With no target set, the two are the same.

Why is my break-even ACOS lower for paperbacks than eBooks?

Paperback royalties are reduced by printing costs, so your royalty is a smaller share of the selling price. Break-even ACOS is exactly that share.

Should I set my bid equal to my break-even CPC?

Your bid is a maximum, and actual CPC is usually lower, so many authors bid somewhat above their target CPC and then watch the average. Judge success by the average CPC you actually pay compared with these limits.

How does a price change affect my limits?

A higher price usually raises royalty, which raises break-even CPC, but it can also lower conversion rate. Re-run the numbers with your new royalty and the conversion rate you see after the change.

What if my conversion rate is 0%?

Then no CPC is profitable, and the calculator says so. Gather more data or fix the product page before spending more.

How is this different from the KDP Break-Even Calculator?

The [KDP Break-Even Calculator](/tools/kdp-break-even-calculator) finds how many copies cover your fixed publishing costs. This tool finds the limits on advertising costs per click and per sale.

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