Free tools for self-publishing authors

No account needed. Built on the same engine PenStranding uses for every book: KDP's rules for 17 Amazon marketplaces, the W3C's EPUB checker, and page measurements from its own typesetting.

• Spine and cover size calculatorEnter your trim size, paper and page count, and get the spine width and the full wrap size KDP expects, in inches and millimetres, for a paperback or a hardcover.
• KDP royalty calculatorPick the format, the marketplace and your list price, and see what KDP pays you per sale, with the printing cost, the lowest price KDP accepts and the royalty plan that applies.
• Page count estimatorType your word count, and see how many pages your book prints at in each trim size, and how wide its spine will be.
• ISBN barcode generatorType your ISBN and download a print-ready barcode for the back cover, as a vector PDF or SVG, or as a PNG.
• EPUB checkerUpload an EPUB of up to 30 MB, and the W3C's EPUBCheck validates it. You see each error and warning with the file and line it points to, and plain words for a dozen common messages.
• Where to sell books in your languageChoose the language your book is written in, and see which stores sell it as an ebook and as a print book, and how to reach each one.