Will M4B to MP3 keep the chapters?

No. MP3 can't hold them. If your player takes M4A, convert to M4A instead and they're kept.

Can I convert a whole 10-hour audiobook to MP3?

In parts: each MP3 can be up to 60 minutes long, so split the book first and convert the parts in one go. If your player takes M4A, convert the whole book to M4A instead — chapters and all.

What MP3 bitrate is best for audiobooks?

128 kbps. Narration doesn't need more, and the files stay small.

All tools

M4B to MP3 Converter

Convert M4B files to MP3 in your browser — nothing is uploaded.

MP3 has no chapters, so they aren't kept. Each MP3 can be up to 60 minutes long — for a whole book in one file, choose M4A, which keeps the chapters.

MP3, WAV, FLAC, M4A, M4B, MP4, AAC, OGA or WEBA, one or many. Drop them here or paste with ⌘V / Ctrl+V. Choose what each becomes on its row.

Runs on your device. Files are read and converted in your browser and aren't uploaded.

M4B

Lossy
Audiobooks
Keeps chapters

An audiobook file: the same AAC sound as an M4A, marked as a book so apps like Apple Books keep your place and show its chapters. Made for long spoken audio rather than music.

M4B Converter — convert M4B files to any format

MP3

Lossy
Plays everywhere
Small files

The audio format almost everything plays. MP3 makes small files by leaving out detail most ears won't miss, which makes it the safe choice for music, podcasts and voice notes you want to share, upload or keep on a phone.

MP3 Converter — convert MP3 files to any format

Learn more about converting M4B to MP3

When you'd do this

Your audiobook is an M4B, but the player you listen on — an older MP3 player, a car stereo, a kids' audio box — only plays MP3.

What to expect

An hour of an audiobook at 64 kbps is about 27 MB as an M4B. As an MP3 at 128 kbps — where this page starts — it's about 55 MB; at 192 kbps it would be about 82 MB with no gain for a voice.

Recommended settings

128 kbps: plenty for narration, and a third smaller than 192. Mix to mono doesn't make a constant-bitrate MP3 any smaller, so leave Channels as they are.

Where it plays

Any MP3 player, car stereo or phone — though without chapters, you'll find your place by time.

Good to know

Chapters aren't kept: only M4B and M4A keep chapters, and an MP3 has nowhere to put them.
Each MP3 made here can be up to 60 minutes long — a handy size on players that list files as tracks. For a longer book, split it into parts first (any audio editor can), or choose M4A: it keeps every chapter and copies the whole book as is, up to 12 hours, with no quality lost.
The book's title, author and cover aren't copied.

How to do it

Choose your M4B files, or drop them on the page — as many as you like.
Each is set to MP3. Change one on its own row if you like, and the MP3 bitrate and the channels in Settings.
Convert all, then download each MP3, or all of them in one .zip.

Questions

Will M4B to MP3 keep the chapters?: No. MP3 can't hold them. If your player takes M4A, convert to M4A instead and they're kept.
Can I convert a whole 10-hour audiobook to MP3?: In parts: each MP3 can be up to 60 minutes long, so split the book first and convert the parts in one go. If your player takes M4A, convert the whole book to M4A instead — chapters and all.
What MP3 bitrate is best for audiobooks?: 128 kbps. Narration doesn't need more, and the files stay small.