For those who have a lot of audiobooks in m4b format, follow one of the methods shown below to transform m4b to mp3.

M4B file format is generally used for audiobooks. Generally, it's used by iTunes to keep audiobooks. The good thing of the M4B file format is it can store bookmarks and chapters in its metadata. However, some apps might not support M4B playback. In those situations, it is simple to convert M4B to MP3.

There are various methods to get it done. I'm sharing the best ways to convert M4B files to MP3 in Windows 10. Follow the one you want.

1. Convert M4B to MP3 with VLC

The VLC media player includes a built-in media converter than can convert media files in one format to another. Since a majority of Windows users already install VLC to experience media files, you don't have to install another software simply to convert m4b to mp3. Remember that this process won't preserve chapters.

Open VLC media player by searching for it in the start menu.
In the navigation menu, visit "Media → Convert / Save" option. You can also make use of the keyboard shortcut Ctrl + R.
Under the File tab, click the "Add" button.
Browse towards the folder in which the M4B file is stored, select it, and click on the "Open" button.
Within the convert window, click on the "Convert" option in the "Convert / Save" drop-down menu.
Now, select the radio option "Convert" and choose "Audio - MP3" in the drop-down menu alongside Profile. Click the "Browse" button to choose the destination to save the converted file.
Visit the folder in which you wish to save the converted file, name the file, and click on the "Save" button. Don't forget to add .mp3 extension to the file name.
In the convert window, click on the "Start" button. This can start the m4b to mp3 conversion process.

Depending on how long the playtime and your system specs, it will take serious amounts of convert m4b file to mp3. For example, the audiobook I'm trying to convert is around 20 hours long. It took about 10 mins to accomplish alteration. While VLC is converting the file, you can see then progress in the media seek bar.

2. FFmpeg command to Convert M4B to MP3

FFmpeg is one of my personal favorite software with regards to media conversion. You can do so much with FFmpeg software. Having a simple FFmpeg command, you can convert M4B file to MP3. Follow the steps below to convert m4b files to mp3 using FFmpeg.

Install FFmpeg and add it to the Windows path, if you haven't already.
Now, open the folder where the m4b file is saved.
Within the File Explorer, Shift + Right-click and choose the "Open PowerShell here" option. Windows 7 and Windows 8 users can choose the "Open command prompt here" option.
In the PowerShell window, execute the FFmpeg command given below. Don't forget to replace the input.m4b file path with the actual m4b file path and output.mp3 file path with the actual mp3 destination.
ffmpeg -i "C:\path\to\input.m4b" -acodec libmp3lame -ar 22050 "C:\path\to\output.mp3"

Just like with VLC media, with respect to the quality, playtime and you system specs, the conversion process will require a while. So, sit back and wait until the operation is complete. You will have your converted mp3 file very quickly.

As needed you are able to split MP3 with FFmpeg too. Particularly ideal for bigger MP3 files.

3. M4B to MP3 converter software

If you have lots of m4b files then utilizing a dedicated converter is fairly handy. That's where Maniac Tool's Free m4a to mp3 converter into play. Though the software says m4a, it's perfectly able to converting m4b to mp3. In addition, the software can preserve chapters. i.e. it automatically converts and splits mp3 files into chapters.

Get the software and install it in your system.
After installing, open the application from the beginning menu.
In the program window, select "Add Files". For those who have multiple m4b files inside a folder, select "Add Files -> Add Folder".
Browse to the folder of your liking, select the m4b file, and then click the "Open" button.
If the added m4b file has chapters inside it, the software asks if you wish to split the file into chapters. Click the "Yes" button to separate the file into chapters.
Now, select all of the files using Ctrl + A.
Select output folder as "Input Folder".
Select output format as "MP3".
Click on the "Convert" button.

As soon as you click the start button, the software starts alteration. The conversion process will require a while with respect to the file size, playtime and system specs. Sit back and wait till the operation is complete. Once done, the converted file(s) are saved in exactly the same folder as the source m4b file.

4. M4B to MP3 Online Converter

When the above methods didn't work for whatever reason or if you don't want to install any software to transform m4b files to mp3, you can use a web-based converter. Keep in mind that nearly every online converter have a quality limitation. If the M4B file is too big, you may not be able to convert it utilizing an online converter.

Go to https://cloudconvert.com/m4b-to-mp3.
Now, drag and drop the m4b files within the browser.
Next click on the "Start Conversion" button. Cloud Converter only supports as much as 1 GB file on their free tier.
As soon as you press the start button, the file is going to be uploaded and the cloud converter will start alteration.
Once done, click the "Download" button to download the converted file.

When compared to above three methods, the internet conversion process might take even more time considering the upload, conversion, and download time.

Wrapping Up Different Ways to Convert M4B to MP3

All the methods shared above work really great. If you have the VLC media player installed and do not mind the loss of chapter data, make use of the VLC media player. Want more control and do not mind the command line then use FFmpeg. If you wish to preserve chapters in M4B files then use Free M4B to MP3 converter. Finally, if you do not wish to install any software or if your need is temporary then use the online converter.

Hope that helps.