How much is your book idea worth?

Unfortunately, there’s no formula to figure out how many copies your book will sell. I wish there was — it would make my job a lot easier.

But I can share how editors make their decisions on how much to give authors as an advance on earnings.

The first thing to know is that when an editor is interested in acquiring the rights to publish a book, she has to run what’s called a P&L.

A P&L, or a profit and loss statement, is exactly what it sounds like. It’s a spreadsheet full of complex formulas. There’s the cost of printing each book, the cost to keep the lights on and pay the salary of everyone at the publisher, the cost to market and publicize the book . . . and so on. An editor has the power to change a lot of variables, but the most important are the amount paid to the author (the “advance”) and the number of copies sold.

In order to acquire a book, the editor needs to make those numbers work. So usually she’ll keep plugging different numbers in until she gets something that she thinks will satisfy everyone involved — the agent and the author (who want the highest advance possible) and the publisher (who wants to sell the most copies possible).

Typically, the biggest variable is how many copies will be sold.