Most indie authors publish in only one language — and reach a fraction of their potential audience as a result. Worth putting some real numbers behind exactly how large that gap is.
Market sizes compared
- German (DE/AT/CH): roughly 130 million speakers, but a strong ecosystem (Tolino, high purchasing power)
- English: roughly 1.5 billion speakers, about 37% of the global ebook market
- Spanish: roughly 560 million speakers, second-largest book market with strong growth
- Portuguese (mainly Brazil): roughly 215 million speakers, audiobook growth of over 45% in recent years
- French: roughly 310 million speakers, with Kobo as the dominant platform in France/Canada
A book that exists only in German reaches, on paper, roughly 130 million potential readers. Add an English translation and it's roughly 1.5 billion — with no additional marketing at all, simply because the book exists in that language.
What that means for the math
A translation is a one-time investment (starting in the low double digits with AI-powered services, considerably more with traditional human translators), and the market access afterward is permanent. In other words: the cost is incurred once, while the potential additional sales run for the entire lifetime of the book.
Worth keeping realistic, though: according to self-publishing surveys from the German-speaking market, most indie authors earn little even in their home market — the large majority under €50 a month. A translation doesn't automatically turn a mediocre-selling book into a bestseller. What it does: it opens an additional channel that, for a book already working in its home market, has the potential to multiply reach — because the English-language market alone is roughly ten times larger than the German-language one.
Who benefits more from this
More likely yes: books that have already found some readership at home, series (where translation cost amortizes across multiple volumes), genres with broadly comparable taste internationally (fantasy, romance, thriller — less culturally bound than, say, a regional mystery with very local references).
Better to wait: the very first book, before it's clear whether it works in the home market at all — gather feedback and sales numbers there first, then think about translation, instead of investing in multiple languages simultaneously from day one.