How to Calculate KDP Ad Profit: ACOS, ROAS, CPC and Break-Even

Why ad profit starts with royalty

Amazon Ads reports sales at the book's list price. You do not receive the list price. You receive the royalty, which for a paperback is the list price times the royalty rate minus the printing cost, and for an eBook is based on the 35% or 70% option. Ad spend comes out of that royalty. This is why a campaign can look healthy in the ads console and still lose money.

Before you analyze any campaign, find your royalty per sale with the KDP Royalty Calculator. Every break-even figure below depends on it.

The core ad metrics

ACOS and ROAS describe the same relationship from opposite sides. An ACOS of 25% equals a ROAS of 4. TACOS is useful once ads start lifting organic sales, because it shows ad spend against everything the book sells, not only the clicks you paid for.

Click-through rate (clicks ÷ impressions) matters too, since it shows whether your cover, title, and price attract clicks. You can check it with the CTR Calculator.

Break-even ACOS and break-even CPC

The break-even point is where royalties from ad-driven sales exactly cover the ad spend. Two formulas find it.

Break-even ACOS = Royalty per sale ÷ List price

Break-even CPC = Conversion rate × Royalty per sale

Break-even ACOS tells you the highest ACOS you can run without losing money on direct sales. Break-even CPC tells you the most you can pay for a click, given how often clicks turn into sales. If your actual CPC is above the break-even CPC, every click loses money on average. You can raise the break-even CPC by improving conversion (a stronger cover, description, reviews, or price) or by earning more royalty per sale.

A related figure is break-even ROAS = List price ÷ Royalty per sale. If ROAS falls below it, the campaign is losing money on direct sales.

Worked example: a $14.99 paperback

Take a paperback priced at $14.99 on Amazon.com with a royalty of $4.39 per copy (a 6 x 9, 300-page black ink book with a $4.60 printing cost earns this at 60%). Assume a 10% conversion rate, a $0.50 average CPC, and $100 of ad spend.

1. Clicks: $100 ÷ $0.50 = 200 clicks.
2. Orders: 200 × 10% = 20 sales.
3. Ad sales: 20 × $14.99 = $299.80.
4. Royalty earned: 20 × $4.39 = $87.80.
5. Profit on direct sales: $87.80 − $100 = −$12.20.

Every line points the same way. Each sale costs $5.00 in clicks but earns only $4.39, so the campaign loses about $0.61 per sale, or $0.061 per click. To break even on direct sales, the CPC would need to fall to about $0.44, or the conversion rate would need to rise above about 11.4%.

If total sales for the period, including organic sales, were $600, TACOS would be $100 ÷ $600 = 16.67%. That can be a healthy figure even when ACOS on its own looks unprofitable, which is why it helps to track both.

What ad reports leave out

The break-even maths covers direct sales only. Some value from ads does not appear in the same report, and some reports lag behind actual activity.

• Read-through. A reader who buys book one may later buy the rest of a series.
• Organic lift. Extra sales can improve rank and visibility, which may bring sales you did not pay for.
• Kindle Unlimited reads. Page reads may be reported differently from sales, depending on the report you use.
• Attribution delays. Sales can be attributed days after the click, so recent data is often incomplete.

These effects can justify running slightly above break-even ACOS for a first-in-series book, but only if you can see the benefit in your own sales data over time. Do not assume it.

Using the numbers to improve campaigns

1. Find your royalty per sale for the format and marketplace you advertise in.
2. Calculate break-even ACOS and keep it next to your campaign data.
3. Estimate conversion rate from at least a few hundred clicks before drawing conclusions.
4. Set bids at or below break-even CPC for campaigns that need to pay for themselves.
5. Pause or lower bids on keywords with high spend and no sales.
6. Review TACOS monthly to see whether ads are lifting overall sales.

The Advertising Break-Even Calculator works out the maximum CPC for a target profit per sale, and the ACOS Calculator checks real campaign results against break-even. These tools show the maths of a campaign. They cannot predict future results, and no calculation guarantees a profit.