About Book Math Tools

Book Math Tools is run by Martins, an independent publisher who sells paperback workbooks on Amazon KDP. The site started as a set of spreadsheets for working out spine widths, printing costs and royalties before each new book, and grew into free tools anyone can use.

How the numbers are checked

Every calculator uses the formulas and rate tables published in KDP's help pages, and each page links to the exact source. The math is covered by automated tests, including the worked examples KDP gives in its own documentation. Rates are re-checked against KDP every month, and each tool shows the date its numbers were last verified.

Independence

Book Math Tools is not affiliated with, endorsed by or sponsored by Amazon or Kindle Direct Publishing. KDP is the final word on your book's numbers, so confirm them in KDP's own calculator before you publish.

Found a mistake or want a calculator that isn't here? Get in touch.