Book Math Tools

Author Income Goal Calculator

Set a monthly income goal and see how many copies that means each month, each day, and per book in your catalog, after ad spend and any Kindle Unlimited income.

Copies a month
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Copies a day
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Per book per day
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Royalties sales must cover
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Yearly income
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The formula

copies a month = (goal + ad spend − other income) ÷ royalty per copy
copies a day = copies a month ÷ 30.42
per book per day = copies a day ÷ books in your catalog

Copies a month are rounded up, since a partial copy pays nothing. A month is taken as 365 ÷ 12 = 30.42 days. The per-book figure assumes sales spread evenly, which they rarely do, but it is a useful sense check: one book selling 10 copies a day is a very different task from ten books selling one each.

Worked example: $1,000 a month

An author sells 75% ebooks at $4.99 ($3.33 royalty) and 25% paperbacks at $14.99 ($4.39), a blended $3.60 per copy.

The total doesn't change, but the second target is far easier to hit, and each book sends readers to the others.

Worked example: a full-time income

A goal of $4,000 a month with eight books, $600 a month from Kindle Unlimited and $800 a month on ads: sales have to cover $4,000 + $800 − $600 = $4,200.00. At $3.60 a copy that is 1,167 copies a month, 38.4 a day, or 4.8 per book per day.

Turning the goal into a plan

The two levers are the number of books and the royalty per copy. Every new book adds a product and gives existing readers something to buy, so adding books is often an easier route to a goal than selling more of one. Royalty per copy moves with price and format: a paperback priced at $9.99 instead of $9.98 crosses KDP's 60% threshold on Amazon.com, and an ebook in the $2.99 to $12.99 band earns 70% instead of 35%.

Ads only help if they sell copies profitably: check the cost per sale against your royalty with the break-even ACoS calculator before raising the budget. And for a series, compare your copies-per-day target with what each new reader is worth across the series in the read-through calculator.

Frequently asked questions

What royalty per copy should I enter?

A blended figure across the formats you sell, weighted by how sales actually split. For example, if 75% of your sales are $4.99 ebooks earning $3.33 and 25% are paperbacks earning $4.39, the blend is 0.75 × 3.33 + 0.25 × 4.39 = $3.60. The format comparison gives each format's royalty.

Is this income before or after tax?

Before tax. KDP may also withhold tax at source depending on your country and tax interview, and you pay income tax where you live. Enter a goal that is your target before tax, or gross it up.

How do I count Kindle Unlimited income?

Enter your monthly KU earnings as other income. They reduce the number of copies you need to sell. The KENP calculator turns pages read into dollars.

Why does the ad spend increase the copies needed?

Ad spend is a cost that sales have to cover before any of the royalty counts toward your goal, so $300 a month of ads at $3.60 a copy means about 84 extra copies a month just to stand still.

Sources

Rates last checked against KDP's help pages on 2026-10-16.

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