Why convert an M4B to MP3?
M4B is the best format for audiobook apps, but plenty of players don’t understand it: older MP3 players, many car stereos, some smart speakers and fitness watches. MP3 plays on almost anything. Splitting by chapter also makes long books easier to manage on devices without proper bookmarks.
M4B to M4A, without re-encoding
Some apps and devices open .m4a but not .m4b, though the audio inside is the same AAC. Choose M4A · Original quality and the audio is copied into an M4A as it is: no generation loss, the same size, and a whole book in seconds, with its chapters kept. Only files with AAC audio can be copied; anything else needs MP3.
Made for a car, CDs or Yoto
Tell the converter where the book will play and it lays the files out for that device:
| Choose | You get |
|---|---|
| Car or USB stick | Numbered MP3 tracks (3 to 30 minutes), plain-letter names, ID3v2.3 and ID3v1 tags, a 500 px cover; folders of 255 tracks for very long books |
| Audio CDs | Tracks of 2 to 15 minutes in disc folders of up to 79½ minutes and 99 tracks, to burn as audio CDs |
| MP3 CDs | Tracks in folders of up to 690 MB, to burn as data discs |
| Yoto cards | Tracks of up to 60 minutes in card folders of up to 100 tracks, 5 hours and 490 MB |
Every chapter starts a new track. A chapter longer than the track length is cut into equal pieces, and each cut moves back into the pause before it, so no track starts mid-word. How to copy, burn and play them: audiobooks on CD, USB and in the car and audiobooks on Yoto.
Choosing a layout
| Layout | Best for |
|---|---|
| Whole book | Phones and apps that remember your place in one long file |
| By chapter | MP3 players and car stereos that skip by file (the splitter has more ways to choose) |
| Equal parts | Books without chapters, or devices that struggle with long files |
What’s kept
Each MP3 gets an ID3 tag with the chapter title, the book as the album, the author, the narrator, the genre, a track number such as 3/24 and the cover art, so the files sort and display correctly on any player.
Quality and size
An hour of speech at 64 kbps is about 29 MB; at 128 kbps it is about 58 MB. Because the source is already compressed, choosing a much higher bitrate than the original won’t make it sound better, only bigger. Check your file’s bitrate in the Audiobook Inspector.