Why royalty ≠ profit
KDP shows you 'estimated royalty' but never your real margin. A $12.99 paperback with a $4.40 royalty looks profitable — until you remember the $1,500 you spent on editing and the $1.50/book you burn on Amazon Ads. Subtracting both can leave you at $1.50 actual profit per book.
Fixed vs variable costs
Fixed launch costs (editing, cover design, formatting, ISBN) are paid once and amortize across all sales. Variable costs (print, delivery, ads, ARC giveaways) recur on every sale. A healthy KDP product earns back its fixed cost within 6–12 months and then runs at high margin for years.
The 30/30/30/10 rule of thumb
Many seven-figure indie authors aim for a cost mix of roughly 30% print, 30% ads, 30% taxes/overhead and 10% net profit on Kindle, with paperback profits subsidizing the ad spend. This calculator helps you check whether your current price/cost mix is close to that target.
Improving your margin
Three levers move margin the most: raise the list price by $1–2, drop ad ACoS below 40% with tighter targeting, and cut print cost by trimming pages. A 10% price increase plus a 10% ACoS drop can double net profit per book without losing meaningful sales velocity.
Frequently asked questions
Is editing cost mandatory?
Not technically, but unedited books almost always fail to recoup their launch cost due to poor reviews.
How do I know my real ad cost per book?
Take your monthly Amazon Ads spend and divide by units sold (ad-attributed plus organic). The calculator uses this blended figure.
What's a good profit margin for KDP?
15–25% net is healthy for indie publishing. Anything above 40% suggests you can scale ads more aggressively.
Should I count my time as a cost?
Yes, internally. For comparison with this calculator, add it as part of the fixed launch cost so payback period reflects opportunity cost.