Calculate Your Ad ROI
1. Your Book
$4.99
The retail price of the book your ad is promoting.
What percentage of the sale price you actually keep. This determines your breakeven ACOS -- pick whichever matches where this ad is sending traffic.
2. Your Ad Campaign
$100/mo
How much you spend on this ad campaign per month. All results below (clicks, sales, breakeven) are monthly figures based on this.
$0.40
What you pay per click, set by your bid and auction competition. Amazon Ads for books commonly runs $0.10-$0.80/click; Facebook/BookBub often $0.20-$1.50. Clicks are calculated automatically as Ad Spend / CPC.
To Break Even on $100/month...
29
Books to Sell
5.7%
Conversion Rate
Ad Performance Analyzer -- Any Platform
Upload or paste your ad performance report from Amazon Ads, Facebook/Meta Ads, Google Ads, BookBub, TikTok Ads, or any platform that exports to CSV. We'll use the Book Price and Royalty Rate from above to tell you instantly which keywords/ads are working, which aren't, which need more time, and what to do about each one.
...or paste below
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⚠ Your Breakeven Math, Explained
At a 70% royalty rate, you breakeven at 70% ACOS -- above that, every sale from ads loses money.
Breakeven by Royalty Rate
| Royalty Rate | Per Sale | Books to Breakeven | Conv. Rate Needed |
|---|
Screenshot and share with a fellow author -- especially if your breakeven number surprised you.
Breakeven figures are estimates based on the inputs you provide. Actual ad performance varies by genre, targeting, bid strategy, and seasonality. Always verify against your platform's own reporting dashboard before scaling ad spend.
Why This Matters
The Mistake Most Authors Make
A low ACOS isn't automatically good, and a high ACOS isn't automatically bad -- it depends entirely on your royalty margin. A 50% ACOS is a losing campaign on a 35% royalty book, but a profitable one on a 70% royalty book. Always compare your ACOS to your own breakeven point, not a generic benchmark.
Author FAQ
ACOS (Advertising Cost of Sale) is the percentage of sales revenue spent on advertising: ACOS = Ad Spend / Ad-Attributed Revenue x 100. A 30% ACOS means you spent 30 cents in ads for every dollar of sales revenue the ad generated. Lower ACOS is generally better -- it means you're spending less to generate each dollar of sales.
Your breakeven ACOS equals your royalty rate. If you earn 70% royalty, you breakeven at 70% ACOS. Most profitable campaigns target an ACOS well below their royalty rate -- often 15-40% -- to leave real profit margin after the ad spend. A 69% ACOS on a 70% royalty book is technically "profitable" but leaves almost nothing after costs like editing and cover design are factored in.
ROAS (Return on Ad Spend) is revenue divided by ad spend -- essentially the inverse of ACOS. A ROAS of 3x means you earn $3 in revenue for every $1 spent on ads. ACOS is the standard metric in Amazon Ads reporting; ROAS is more common on Facebook, Meta, and BookBub ad platforms. You can convert between them: ROAS = 1 / (ACOS as a decimal).
Profit = (Sales from ads x royalty per sale) - Ad Spend. If that number is positive, your campaign is profitable. The part most authors miss: profitability depends on your royalty margin, not just your ACOS or ROAS in isolation. A 50% ACOS can be solidly profitable at a 70% royalty rate, but a straight loss at a 35% royalty rate -- always check your numbers against your specific breakeven point, not a generic industry benchmark.
Why is my conversion rate lower on Facebook/BookBub than Amazon Ads?
Amazon Ads keep the shopper inside Amazon's own ecosystem with one-click purchasing already set up -- conversion rates of 5-12% are common. Facebook and BookBub ads send traffic off-platform to a retailer page, adding friction (the click, the load time, re-entering payment info) that typically drops conversion to 1-5%. This is normal and doesn't necessarily mean the ad itself is performing poorly -- it's a structural difference in the funnel.
Should I pause a campaign with a high ACOS?
Not necessarily right away. New campaigns often run a high ACOS during the "learning phase" as the algorithm figures out which keywords/audiences convert. Many authors run ads intentionally above breakeven short-term to boost a book's sales rank or gather reviews, treating the ad spend as a visibility investment rather than pure immediate profit. The key is knowing your breakeven number and making that tradeoff a deliberate choice, not an accident.
Sources & Reference
Amazon Ads ACOS Guide
KDP Advertising Help
Meta Ads Cost Guide
BookBub Partner Insights