KDP book ads bid calculator: what CPC meets your profit target?

Use a book's net royalty per sale, a purchase-rate assumption, and a profit target to check what average CPC could leave you the amount you want. Maximum CPC = (royalty per sale − target profit per sale) × purchase rate. The purchase rate is attributed purchases divided by ad clicks; use it as a fraction in the formula, so 10% is 0.10. This tool floors the result to a whole cent and checks an entered average CPC against it; it does not set or recommend an Amazon auction bid.

Add ad-attributed sales value per purchase if you also want to compare modeled ACoS with your target. That sales value is different from your royalty.

Net KDP royalty after KDP deductions and before ads, for one sale.
Estimate royalty
Your chosen amount left per ad-attributed sale after ad cost.
Attributed purchases divided by ad clicks. Enter a percent; the % sign is shown after this field.
Planned or observed average cost per click, not the Amazon auction bid.
Optional ACoS revenue denominator per purchase. This is sales value, not royalty or list price.

Enter a royalty, purchase-rate assumption, and average CPC to check the bid. All amounts should refer to the same book and one attributed purchase. ACoS appears only when you enter ad-attributed sales value.

How to use the bid check

  1. Enter the net KDP royalty for one attributed book sale, after KDP deductions and before advertising. If you need an estimate, start with the KDP royalty calculator. If you want the target to cover other per-copy costs too, subtract them from the amount you enter.
  2. Enter the amount you want to keep per sale, your expected or reported purchase rate, and the planned or observed average CPC. For example, enter 10.00 for a 10% purchase rate. Use a rate from your own Amazon Ads report for a retrospective check; a rate you choose for a future campaign is an assumption.
  3. Read the maximum whole-cent CPC, the verdict for your entered CPC, the modeled amount left per attributed sale, and the minimum purchase rate your CPC would need to meet the target. These are conditional on the royalty and purchase rate you entered.
  4. To see ACoS, enter the ad-attributed sales value per purchase you want to compare with the modeled cost. It is sales revenue, not royalty or automatically the book's list price. Leave it blank when you only need the CPC check.

If you edit an input after a result appears, the old comparison clears until you check the updated assumptions. Blank required fields or invalid numbers show a field error; a blank optional sales value simply leaves out ACoS.

How the CPC ceiling works

The royalty is the amount available from a sale before advertising. Subtract the amount you want to keep to find the most you can spend on ads for that sale. The purchase rate turns that per-sale headroom into an average cost per click. The calculator floors the result to cents, so its maximum does not round above your target.

Check a planned average CPC

With a $4.39 royalty, a $1.00 target, and a 10% purchase rate, the available ad cost is $3.39 per attributed sale. The raw CPC ceiling is $3.39 × 0.10 = $0.339, so the highest whole-cent average CPC that stays within the target is $0.33. At an entered average CPC of $0.30, the model gives $3.00 in ad cost per attributed sale, leaving $1.39 from the royalty. The entered CPC meets the target under these assumptions.

The purchase rate is not a promise that future clicks will convert. A rate taken from a campaign report follows that report's attribution method; a rate you choose for planning remains an assumption. The required purchase rate is the minimum rate that would make the entered CPC fit the target, rounded up to two decimal places. A required rate above 100% cannot be reached within the model.

ACoS and author profit answer different questions

Amazon Ads defines ACoS as advertising spend divided by ad-attributed sales revenue. In the example above, if the sales value is $14.99 per attributed purchase, $3.00 in modeled ad cost per sale is a 20.0% ACoS. The target's $3.39 ad-cost ceiling is a 22.6% ACoS ceiling at that sales value.

When a target cannot be met

At 0% purchases, the model assumes the clicks produce no attributed purchases. It cannot show a per-sale amount, an ACoS at the entered CPC, or a meets/misses verdict. A positive CPC at that assumption spends without an attributed purchase.

If the target is higher than the royalty, even a $0.00 CPC leaves too little to meet it. The calculator has no CPC ceiling or required purchase rate for that case. If the required purchase rate is higher than 100%, it is unattainable within the entered range. These states are different from a missing or invalid input, which must be corrected before the calculator can return a result.

Use your own royalty and campaign data

For a planned calculation, use a KDP royalty estimate and label a future purchase rate as an assumption. For a retrospective comparison, use average CPC, attributed purchases, and sales value from your own Amazon Ads reporting. This tool does not connect to your account, import campaign activity, or verify attribution. It does not include series read-through, Kindle Unlimited reads, organic lift, taxes, refunds, or costs you have not included in the royalty or target.

Read Amazon Ads' ACoS definition, its advertising metric guide, purchase-rate reporting definition, and Sponsored Products guidance for authors when checking campaign terms. Use the KDP royalty calculator to estimate a royalty per sale, then compare an observed result with your Ads report.