My contract says “author royalty 70%”. What goes into the store cut field?

Put 30%. The field asks what share of the price the store takes, not what it leaves you. If the author royalty is 35%, the field takes 65%.

How do I calculate an ebook?

Put zeros in the three printing fields: fixed part, page price and page count. What remains is the store cut and the file delivery fee that some platforms charge separately. The “Example: ebook” button fills in exactly that set.

Why does the ISBN field start at zero?

Because on KDP you do not have to buy one. An ebook gets a free ASIN, and a paperback can take a free KDP-issued ISBN. The catch is that the imprint on a free ISBN is not yours. A single ISBN bought in your own name costs about 125 in the US, and blocks of ten or more bring the price per number down sharply. If you want your own imprint, put that figure into the field.

Why is the break-even point higher than the costs divided by the price?

Because you have to divide by what is actually left of the price, not by the price. Out of a price of 12.99, after a 30% commission (3.90) and 3.49 of printing for a 220-page paperback, 5.60 is left, and after 5% returns it is 5.15. Dividing the 1,020 of one-time costs by that gives 199 copies — not the 79 you would get by dividing by the price.

The tool says “never recouped”. What does that mean?

That at the current price every copy sold takes money away: commission, printing and returns together exceed the price. A larger print run does not help here, because more sales only make the loss bigger. You need to raise the price, cut the unit cost, or change the channel.

How much can I trust the “profit per month” column in the neighbouring rows?

Exactly as much as you trust your own sensitivity slider. It is not a market forecast but a consequence of your guess. The useful part here is not the number itself but how much it moves when you move the slider.

No. Profit in this calculator is before tax. How much of it to set aside is handled by the separate “Freelance taxes: how much to set aside” tool.

Book price and break-even point

This calculator shows how much the author keeps from one copy sold, how many copies you have to sell to get back the money you put into the edition, and how many months that takes at your own pace of sales. It is a tool for a self-publisher who has already paid for the cover, the editing and the typesetting and is now setting a price. It does not guess demand for you: wherever a guess is unavoidable, you enter the number yourself and see at once how much the conclusion depends on it.

Your numbers

One-time publishing costs

Cover A pre-made cover with your title dropped in runs about 150; a custom illustrated one costs several times that.

Editing A light copy edit of a mid-length manuscript. Developmental editing is a different service and costs far more.

Proofreading

Typesetting

ISBN and registration Zero by default: KDP hands out a free ASIN, and a free KDP-issued ISBN for print. A single ISBN bought in your own name runs about 125 in the US — put that here if you want the imprint to be yours.

Launch advertising

These six sums add up to one figure, and that is what sales have to earn back. Put zero wherever you spent nothing.

Cost of a single copy

Printing: fixed part The per-copy charge that does not depend on length. 0.85 is the KDP US black-and-white paperback figure at the time of writing — check it against the current KDP printing-cost table.

Printing: per page KDP US black-and-white on white paper. Colour interiors cost several times more per page.

Pages in the book

For an ebook put zeros in all three fields: there is no printing, only the store cut remains.

Sales channel and the cut

Sales channel Picking a channel fills typical values into the two fields on the right. Correct them to match your contract; nothing is locked.

Store keeps, % If the contract says “author royalty 70%”, put 30 here. On KDP that is the ebook case; a paperback pays the author 60%, so the store keeps 40.

File delivery fee What the platform charges to hand the file to the buyer — on KDP roughly 0.15 per megabyte on the 70% rate, so a 2 MB book costs about 0.30. For print books this is zero.

Price and sales

Price for the buyer

Sales per month Your own expectation, not a market forecast.

Returns, %

Currency Only a label: dollar, pound and euro are printed before the number, hryvnia and zloty after it. The tool pulls no exchange rates, so keep every field in one currency.

Your guess: by what % demand falls when the price goes up by 10%

0% — demand ignores the price 15% 40% — the buyer is very price-sensitive

This is your assumption, not a measured property of the market. The tool does not know your audience; it only shows honestly what follows from the number you set. Move the slider and see how much the conclusion depends on it.

What this comes to

— profit from one copy sold

— break-even point, copies

— months to recoup at your pace

—one-time costs in total

—variable cost per copy

—profit per month at your pace

—share of the price that stays with you

Costs covered

— —

How much of the one-time costs a single month of sales covers at the pace you entered.

Price scenarios

Price	Profit per copy	Break-even, copies	Sales per month	Profit per month
Fill in the price and the costs and five scenarios will appear.

Five points around your price: minus 30%, minus 15%, your price, plus 15%, plus 30%. The sales figure in every row is recalculated from the sensitivity slider, that is, from your assumption and not from market data.

The numbers never leave your browser: everything is calculated on your device, nothing is sent anywhere and nothing is stored.

How profit per copy is calculated

First everything that each individual sale takes away is subtracted from the price: the store share in percent, the file delivery fee and the printing cost. The printing cost is the fixed part per copy plus the per-page cost multiplied by the number of pages. Then returns come into play. A returned copy is not simply one sale less: the buyer gets the money back in full, while the printed book has already been paid for at the printer. So the expected profit is the share of copies that stay sold multiplied by the net profit, minus the share of returned copies multiplied by the printing cost. The one-time costs — cover, editing, proofreading, typesetting, ISBN, launch advertising — are added into a single sum and divided by the profit per copy. The result is the break-even point: that is how many books you have to sell to come out level. The figures the tool opens with are a modest US indie set in dollars: 150 for a cover, 400 for a copy edit, 150 for proofreading, 120 for typesetting, nothing for the ISBN, 200 for the launch — 1,020 in total. The printing line matches KDP's US black-and-white paperback: 0.85 fixed per copy plus 0.012 a page, which is 3.49 on a 220-page book. The price is 12.99 and the store cut 30%. None of that is a quote for your book; it is a starting point you are expected to overwrite.

Why there is a scenario table, and what the slider means

A single price tells you nothing. The real question is always different: what happens if you go cheaper, and what happens if you go dearer. The table shows five points — minus 30%, minus 15%, your price, plus 15% and plus 30% — with the profit, the break-even point and the monthly earnings for each. To work out the monthly earnings at the neighbouring points you need to know how demand will change. Nobody knows that, so the tool invents nothing: you set with the slider by what percentage demand falls when the price goes up by 10%. The default is 15%, which is simply a moderate starting point and not a measured property of the book market. Move the slider from 5% to 30% and watch which row is the most profitable. If the conclusion flips after a small move of the slider, the pricing decision rests on a guess rather than on a calculation, and it is better to know that in advance.

Why the sales channel changes everything

A marketplace or a large bookstore keeps a noticeable share. On KDP that is 30% of the list price for an ebook inside the 70% royalty window, and 40% for a paperback, where the printing cost comes off on top of that; other contracts go higher still. Your own site leaves you almost the whole price, but the payment service takes its own percentage too, and traffic to the site has to come from somewhere, with its cost usually hidden in the advertising line. Offline — fairs, reader meetings, bookshops — is often the most expensive in terms of the share the middleman takes, but it sells a print book at a higher ticket and without advertising. Picking a channel in the tool only fills typical values into the store cut and delivery fields. Correct them to match your contract: no template knows what was actually signed with you.

What this calculator does not do

It does not forecast demand. Sales per month is your number, and the model of how demand reacts to price is your slider. The tool only carries both assumptions honestly through to a conclusion instead of hiding them inside. It does not calculate taxes; there is a separate reserve calculator for that. It ignores exchange rates: the currency selector only chooses a symbol and where it is printed — before the number for the dollar, the pound and the euro, after it for the hryvnia and the zloty — so every field has to be in the same currency. It knows nothing about marketplace discounts, promotional weeks, rights reverting, or a reprint in a smaller run at a different price. And it looks at price only from the cost side. What a reader is willing to pay for a book of your particular genre and length is a question for the market and for your audience, not for arithmetic.

Book price and break-even point

How profit per copy is calculated

Why there is a scenario table, and what the slider means

Why the sales channel changes everything

What this calculator does not do

Frequently asked questions