M4B to MP3 Converter
M4B is the audiobook flavor of MPEG-4 audio, with chapters and a bookmark built in for Apple Books. Outside Apple's apps those extras are often ignored and the file itself may not open, so many listeners convert audiobooks to MP3.
Audio Converter
or drop MP3, WAV, M4A … files here ·
Max 95 MB per file· Up to 20 files· Deleted after 30 minutes
Files are processed on our servers and deleted after 30 minutes.
Constant bitrate (CBR) gives a predictable size and works on every player. Variable bitrate (VBR) spends bits where the music needs them and is usually smaller at the same quality.
Keep the source rate unless a device asks for one. 44.1 kHz is CD standard, 48 kHz is video standard, 8 kHz is used by phone systems and AMR.
Mono halves the size of lossless files and is fine for voice recordings.
16-bit is CD quality. 24-bit keeps headroom for editing and mastering; converting a 16-bit source up does not add detail.
Optional. Seconds (e.g. 75) or minutes:seconds (1:15). Leave empty to start at the beginning.
Optional. Same format as the start time. Leave empty to keep everything up to the end.
How to use this tool
- 1
Add the M4B audiobook
Upload DRM-free .m4b files up to 95 MB each, up to 20 at a time. Books split into several parts can go in one batch.
- 2
Keep the speech settings
The page uses 64 kbps and Mono, the usual audiobook quality. Choose Stereo and 96 kbps only for a dramatized production with music and effects.
- 3
Press Convert to MP3
Each file becomes one MP3 with title, author and cover art. Download them separately or as a ZIP; uploads are deleted after 30 minutes.
Upload a DRM-free .m4b file and press Convert to MP3. The speech settings preset here, 64 kbps mono, keep a narrated book clear at about 29 MB per hour; chapter markers do not carry over, so split long books with Start at and End at if you need chapters as files.
What an M4B audiobook file is
An M4B file is an ordinary MPEG-4 audio file, usually AAC, with a different extension. The "b" stands for book: it tells Apple's apps to remember the listening position, show the chapter list and keep the file out of the music shuffle. Many audiobook tools that bundle a whole book into one file write M4B, and LibriVox offers it for public-domain recordings.
The trouble is everything outside the Apple world. A car stereo that reads a USB stick usually looks only for .mp3 and .wma, a basic clip-on MP3 player may not decode AAC at all, and some Android players hide .m4b files from their library. MP3 removes those dead ends. For songs and voice memos in the same container but with the .m4a extension, use M4A to MP3.
What you lose: chapters and bookmarks
Chapter markers are not copied to the MP3
MP3 has an ID3 chapter frame, but few players read it, and the converted file is written as one continuous track. Note the chapter times before converting if you need them, or make one MP3 per chapter with Start at and End at.
M4B to MP3 converter: size by book length
| Book length | 64 kbps mono | 96 kbps | 128 kbps |
|---|---|---|---|
| 1 hour | ≈ 29 MB | ≈ 43 MB | ≈ 58 MB |
| 2 hours | ≈ 58 MB | ≈ 86 MB | ≈ 115 MB |
| 3 hours | ≈ 86 MB | ≈ 130 MB | ≈ 173 MB |
| 6 hours | ≈ 173 MB | ≈ 259 MB | ≈ 346 MB |
Narration does not need music bitrates. A single voice at 64 kbps mono sounds the same as the AAC original to most listeners, and it keeps a six-hour book under 200 MB, small enough for an old phone or a cheap USB stick. Raise the bitrate only for full-cast productions with a score.
Two other settings help in the car: Normalise volume evens out chapters recorded on different days, and leaving Sample rate on Same as source avoids needless resampling. If you also want the text of a chapter, audio to text can transcribe the MP3 afterwards.
M4B and MP3 format facts
M4B
MPEG-4 audiobook
M4B is an audiobook format based on MPEG-4 audio, usually AAC, popularised by Apple's iTunes and Books apps. It supports chapter markers, cover art and remembering the playback position, which suits long recordings. Some books from stores are DRM-protected and play only in their own apps. Many generic music players and car stereos do not recognise M4B.
- Compression
- Lossy
- Transparency
- –
- Animation
- –
- Introduced
- Apple
MP3
MP3 audio
MP3 (MPEG-1 Audio Layer III) is a lossy audio format developed largely at the Fraunhofer Institute and standardised by MPEG in 1993. It removes sounds the ear is unlikely to notice, shrinking music to about a tenth of CD size at 128–320 kbps. All patents have expired, and every phone, car stereo, browser and media player supports it. Quality loss is audible at low bitrates and accumulates with re-encoding.
- Compression
- Lossy
- Transparency
- –
- Animation
- –
- Introduced
- 1993 · Fraunhofer IIS / MPEG
M4B audiobooks are built for Apple Books, but car stereos, simple MP3 players and many Android apps either skip the .m4b extension or ignore its chapters, so listeners convert DRM-free books to MP3 to play them anywhere.
Audiobook conversion questions
Can I convert an Audible or Apple Books audiobook?
Not if it is copy-protected. Audible's .aa and .aax files and audiobooks bought in Apple Books carry DRM, and they cannot be decoded here. DRM-free M4B files, such as public-domain recordings from LibriVox or books you encoded from your own CDs, convert normally.
My audiobook is bigger than 95 MB. What can I do?
Each upload is limited to 95 MB, which for an M4B encoded at 64 kbps is about three and a half hours of audio; leaner 32 kbps books fit about twice that. Many stores and libraries supply long books in parts; upload the parts together. A single larger file has to be split with another tool first.
Will the MP3 remember where I stopped listening?
Remembering your place is a player feature. Apple Books does it automatically for M4B; for MP3, use an audiobook or podcast app that saves the position per file. Most dedicated audiobook apps on Android and iPhone do.
How do I make one MP3 per chapter?
Look up the chapter start times in your player, then convert once per chapter with Start at and End at set to that range, for example 1:02:15 to 1:41:30. Number the downloads so they play in order.
Does the cover image come across?
Yes. With Keep tags and cover art on, the artwork, book title and author are written into the MP3's ID3 tags, so car displays and phone apps show the right cover.
- M4A to MP3 ConverterConvert M4A files from iPhone Voice Memos or iTunes to MP3 that plays in any car, app or upload form. Free, no sign-up, 20 files per batch.
- AAC to MP3 ConverterConvert raw .aac files from call recorders, voice apps, dashcams and stream captures to MP3 with correct length and seeking. Free, 20 files at once.
- MP3 to M4A ConverterConvert MP3 songs, lectures and recordings to M4A (AAC) for Apple apps, upload forms and smaller files. Pick the bitrate, keep tags and cover art.
- FLAC to MP3 ConverterTurn FLAC albums into 320 kbps MP3 copies for phones, car stereos and Apple Music, with tags and cover art carried over. Up to 20 tracks per batch.
- WAV to MP3 ConverterConvert WAV recordings and bounces to MP3 at 320, 192 or 128 kbps. Cut file size by up to 90% for email, uploads and phones. Free, no account.
- MKA to MP3 ConverterConvert MKA (Matroska audio) to MP3. AC-3, DTS, FLAC, Opus or AAC inside is decoded and surround is downmixed to stereo. Up to 20 files, 95 MB each.