Convert MP3 to AMR — Free Online Converter
Convert MPEG Audio Layer 3 (.mp3) to Adaptive Multi-Rate Audio (.amr) online for free. Fast, secure audio conversion with no watermarks or registratio...
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Upload your .mp3 file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .amr file when it's ready.
About MP3 to AMR Conversion
AMR (Adaptive Multi-Rate) is the voice codec designed for GSM cellular networks, operating at extremely low bitrates between 4.75 and 12.2 kbps. It was built for one purpose: encoding human speech efficiently enough to transmit over 2G mobile networks with limited bandwidth. Converting MP3 to AMR is a specialized operation typically needed for telephony systems, feature phone compatibility, or speech processing pipelines that require AMR input.
This conversion involves a dramatic quality reduction. MP3 files typically encode at 128-320 kbps across the full audible frequency range (20 Hz to 20 kHz), while AMR-NB operates at 8 kHz sample rate with a 300-3400 Hz bandwidth. The result sounds like a telephone call — adequate for intelligible speech but completely unsuitable for music. This conversion only makes sense when the target system specifically requires AMR format.
Why Convert MP3 to AMR?
AMR remains the standard voice codec for GSM networks, VoIP telephony systems, and Interactive Voice Response (IVR) platforms worldwide. If you need to deploy pre-recorded audio prompts for a phone system, the prompts must typically be in AMR format. Similarly, feature phones from Nokia, Samsung, and Motorola that predate the smartphone era use AMR as their native voice recording and ringtone format.
Speech recognition engines and voice analysis tools sometimes require AMR input specifically. Telecoms testing equipment, call center quality monitoring systems, and cellular network analysis tools process AMR files because that is the format voice calls use over the air. Converting your MP3 voice recordings to AMR feeds them into these specialized systems without format compatibility issues.
Common Use Cases
- Create IVR voice prompts for telephony and call center systems
- Prepare audio for Nokia and Motorola feature phones that only play AMR
- Feed voice recordings into telecoms testing or speech analysis equipment
- Generate ultra-small audio files for embedded systems with severe storage limits
- Send voice messages over GSM networks that require AMR encoding
How It Works
FFmpeg decodes the MP3 source and re-encodes using the libopencore-amrnb encoder at 8 kHz mono with the AMR-NB codec. Output bitrate is selectable from 4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.2, or 12.2 kbps — the standard AMR-NB mode set. The output file uses the simple AMR file format with a #!AMR\n magic header. Stereo MP3 sources are downmixed to mono since AMR only supports single-channel audio.
Quality & Performance
Extreme quality reduction is expected. AMR-NB at 12.2 kbps captures only the 300-3400 Hz frequency band at 8 kHz sample rate, producing telephony-grade audio. All bass below 300 Hz and all treble above 3400 Hz is discarded. Music converted through this path will be unrecognizable. Speech remains intelligible but gains the characteristic narrow, filtered sound of a phone call. This conversion should only be used when the target system requires AMR.
Device Compatibility
| Device | MP3 | AMR |
|---|---|---|
| Windows PC | Native | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Native | Partial |
| Linux | Partial | Partial |
| Web Browser | Native | No |
Recommended Settings by Platform
Spotify
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Apple Music
Resolution: N/A
Bitrate: 256 kbps
AAC format required
SoundCloud
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Podcast
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
Tips for Best Results
- 1Only use this conversion when the target system specifically requires AMR format
- 2Use 12.2 kbps mode for the best AMR quality — lower modes degrade speech noticeably
- 3Ensure your source MP3 contains speech, not music — music is destroyed by AMR encoding
- 4For wider bandwidth voice, request AMR-WB output if the target device supports it
- 5Test the AMR output on your target telephony system before batch-converting
Related Conversions
MP3 to AMR is a niche conversion for telephony, IVR systems, and legacy mobile devices. The dramatic quality reduction makes it unsuitable for music or general listening, but it produces the ultra-compact files that specialized voice systems require.