MP3 to AMR Converter
AMR was designed to squeeze a phone call through a mobile network, and it still makes the smallest voice files of any format here. Turn an MP3 into AMR when a basic phone, an MMS message or a telephony system needs speech in that exact format.
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
Upload the MP3
Add up to 20 MP3 files. Spoken recordings, prompts and short sound clips work best; full songs will sound thin.
- 2
Trim and level
Sample rate is 8 kHz and Channels is mono, the narrowband AMR layout. Under Advanced settings, set Start at and End at to keep only the part you need; Normalise volume is already on.
- 3
Convert to AMR
Press Convert to AMR and download the .amr files. They are small enough to send over any connection.
AMR shrinks a minute of speech to about 90 KB by keeping only the telephone voice band. Use it for words, not music, and keep the MP3 as your master.
Why convert MP3 to AMR
MP3 at 128 kbps spends most of its bits on sound a voice never makes. AMR spends its 12.2 kbps on the part of the spectrum speech lives in, which is why mobile networks used it for GSM and 3G calls and why handsets saved voice memos with it for years. When the destination is built around that codec, a converted file just works where an MP3 would be refused or would be too large.
Typical destinations are a feature phone that takes AMR as a ringtone or message tone, an MMS where every kilobyte counts, an embedded device that plays prompts from its memory, and app or telephony testing where engineers need real AMR input. The audio converter covers other speech formats if none of these is your case.
1999
AMR adopted
3GPP makes Adaptive Multi-Rate the speech codec for GSM and 3G.
2001
AMR-WB
A 16 kHz wideband version follows for clearer voice.
2002
RFC 3267
The IETF defines the .amr storage format that files still use.
2002
ITU-T G.722.2
AMR-WB is approved as an ITU standard, later sold as HD Voice.
MP3 to AMR converter: file size per minute
≈ 92 KBper minute of speech at AMR-NB's top mode of 12.2 kbps
Getting clear speech out of an AMR file
| Do | Don't |
|---|---|
| Start from the cleanest MP3 you have, at 128 kbps or more | Expect background music under a voice to survive |
| Trim silence at the start and end with Start at and End at | Convert stereo music for a ringtone and expect fidelity |
| Keep Normalise volume on so quiet recordings stay audible | Delete the MP3 after converting |
| Play the result on the target phone before sending a batch | Raise the sample rate above 8 kHz for narrowband AMR |
MP3 and AMR side by side
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
AMR
Adaptive Multi-Rate audio
AMR is a lossy speech codec adopted by 3GPP in 1999 for GSM and 3G mobile phone calls. It is optimised for voice at very low bitrates, so music sounds poor. Many phones save call recordings and voice memos as AMR files. Browsers, iPhones and many desktop players do not support it.
- Compression
- Lossy
- Transparency
- –
- Animation
- –
- Introduced
- 1999 · 3GPP (Ericsson, Nokia, Siemens)
MP3 is where most voice clips and prompts start, but feature phones, MMS messages and some telephony test setups were built for AMR's speech codec, which carries the same words in about a tenth of the space.
MP3 to AMR: questions
Why does music sound so bad as AMR?
Narrowband AMR keeps only the frequencies of a telephone line, roughly 300 to 3,400 Hz, and models sound the way a human voice is produced. Speech stays clear, but cymbals, bass and stereo width disappear. For a song ringtone on an iPhone, use MP3 to M4R instead; for a small music file, use Opus or AAC.
Which phones play .amr files?
Most Nokia, Samsung and other feature phones of the 2000s, many current basic phones, and Android, which has decoded AMR since its first release. iPhones and most desktop browsers do not open .amr files directly, so test on the receiving device before converting a large batch.
What is the difference between AMR-NB and AMR-WB?
Narrowband AMR samples at 8 kHz and runs from 4.75 to 12.2 kbps; wideband AMR samples at 16 kHz and runs from 6.6 to 23.85 kbps, giving HD Voice quality. Files made here are narrowband .amr, the variant older phones and MMS readers expect.
Can I use an AMR file as a voicemail or on-hold greeting?
Only if the phone system's documentation lists AMR. Many business systems want 8 kHz WAV instead, which you can make by choosing WAV under Convert to with Sample rate at 8 kHz. AMR is more common on handsets than on PBX servers.
Will converting back from AMR to MP3 restore the quality?
No. The detail AMR removes is gone for good, so keep the original MP3. The AMR to MP3 page is for recordings that started life as AMR, not for undoing this conversion.
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