Free tools for M4B to MP3
- 1
FFmpeg — single file conversion
Convert the whole M4B to one MP3: `ffmpeg -i audiobook.m4b -c:a libmp3lame -q:a 2 output.mp3`. -q:a 2 is LAME's VBR setting of about 190 kbps. For speech, a fixed 64 kbps is plenty and about 29 MB per hour: `-b:a 64k`. FFmpeg keeps the chapter marks as ID3 chapter tags, which podcast apps and some players show.
- 2
m4b-tool (one MP3 per chapter)
m4b-tool splits a book into one MP3 per chapter: `m4b-tool split --audio-format mp3 --audio-bitrate 64k audiobook.m4b`. The files land in a new folder next to the book. Install it with Docker (sandreas/m4b-tool) or on a Mac with Homebrew: `brew install sandreas/tap/m4b-tool`. It needs FFmpeg.
- 3
iTunes (Windows, or macOS Mojave and earlier)
Set Edit → Preferences → General → Import Settings to MP3 Encoder (on a Mac, iTunes → Preferences). Then select the audiobook and choose File → Convert → Create MP3 Version. On macOS Catalina and later, audiobooks live in Apple Books, which can't convert; use FFmpeg or m4b-tool there.
- 4
FFmpeg chapter split (advanced)
List the chapters: `ffprobe -print_format json -show_chapters audiobook.m4b > chapters.json`. Cut each one by time: `ffmpeg -i audiobook.m4b -ss 0 -to 2340.5 -c:a libmp3lame -q:a 4 chapter_01.mp3`. Repeat for each chapter with the start and end times from the JSON.
Why convert M4B to MP3?
M4B is Apple's walled garden for audiobooks. MP3 plays on every device without proprietary software — the right format for listening anywhere.
Frequently asked questions
Do chapter markers survive M4B to MP3 conversion?
What bitrate should I use for audiobook MP3?
Can I play M4B files on Android?
No account. No upload. Works in any browser.