Multiple Formats

AAX Audio Converter supports converting your Audible audiobooks to multiple standard audio formats:

File Size Considerations

The size of your converted audiobook will depend on:

• Original audiobook length
• Chosen bitrate (default: 128kbps)
• Output format
• Chapter preservation

As a general guideline:

• A 10-hour audiobook at 128kbps MP3 ≈ 550MB
• Same audiobook in M4B format ≈ 650MB
• Same audiobook at 256kbps ≈ 1.1GB

Supported Formats

MP3

• Most widely compatible format
• Works with virtually all media players and devices
• Good balance of quality and file size
• Default format if none specified

M4A

• Apple's standard audio format
• Better quality than MP3 at the same bitrate
• Native support on Apple devices
• Smaller file size than M4B

M4B

• Apple's audiobook format
• Includes chapter markers and metadata
• Native support on Apple devices
• Perfect for Apple Books and iTunes

Usage

You can specify the output format using the --format or -f option:

# Convert to MP3 (default)
aax convert audiobook.aax

# Convert to M4A
aax convert audiobook.aax --format m4a

# Convert to M4B
aax convert audiobook.aax --format m4b

Format Comparison

Format	Quality	File Size	Chapter Support	Device Compatibility
MP3	Good	Medium	Yes	Excellent
M4A	Better	Small	No	Good
M4B	Best	Large	Yes	Good

TIP

For the best experience on Apple devices, we recommend using M4B format as it provides the best integration with Apple Books and iTunes.