Free online FB2 to M4A converter

Some phones, car systems, and audio players accept M4A audiobooks but cannot open FB2 ebooks. Converting FB2 to M4A therefore means synthesizing the book’s text as speech and saving the audio, not simply changing the file extension.

What the FB2 format is

FB2 (FictionBook 2) is an XML-based ebook format that stores a book’s text and structure, such as chapters, titles, and author information. It is used for digital books and is supported by ebook readers and library programs, including Calibre; files often come from ebook libraries or older reading-device collections. FB2 contains no recorded narration.

What the M4A format is

M4A is an audio file container commonly used for AAC-encoded sound. It is supported by many phones, media players, and car systems. For a spoken book, AAC in M4A can provide smaller files than uncompressed audio while retaining suitable speech quality.

How to convert FB2 to M4A

Because FB2 is an ebook, conversion uses text-to-speech (TTS) to create narration, then stores that audio in M4A. The generated voice is synthetic; it does not recover an original audiobook recording.

Online on 101convert.com

1. Upload the FB2 file on the converter page. You can add several files for batch conversion; each file is subject to the size limit shown on the page.
2. Before converting, choose the voice language and reading speed.
3. Start the conversion and download the resulting M4A file.

Offline with desktop software

A free, offline workflow uses Calibre to extract the book text, eSpeak NG to synthesize speech, and FFmpeg to encode it as M4A. These tools are available for Linux, macOS, and Windows. Install them, then run the commands in a terminal or command prompt:

1. Convert the FB2 book to plain text: ebook-convert book.fb2 book.txt.
2. Synthesize the text as a WAV file. Replace en with a supported voice language code; adjust 160 to change the reading speed: espeak-ng -v en -s 160 -f book.txt -w speech.wav.
3. Encode the speech as AAC audio in an M4A container: ffmpeg -i speech.wav -c:a aac -b:a 96k book.m4a.

Long books can take time to synthesize and produce large intermediate WAV files. The plain-text step may omit or simplify formatting, and TTS may read headings or other text that a human narrator would handle differently.

Quality and compatibility

Speech quality depends on the selected TTS voice and language, not just the AAC bitrate. Check the output on the intended player, especially for language support and playback of long files. The M4A file contains synthesized narration; it does not retain FB2 chapter navigation or ebook formatting.