AMR to MP3 Converter

AMR (Adaptive Multi-Rate) is the speech codec of mobile phones: old voice recorders, call recordings, MMS voice messages and many Samsung .3ga files use it. Most computers, players and editors cannot open AMR, so this tool converts it to MP3 in your browser. The AMR decoder is part of the ffmpeg engine, a one-time download of about 30 MB; your recordings are never uploaded.

How to use this tool

1. Choose one or more .amr, .awb or .3ga files.
2. Keep 64 kbps and 22.05 kHz for voice, which plays everywhere; choose more only if you need it.
3. Press Calculate.
4. Play the MP3 here and download it, or all files as a ZIP.

Formula

MP3 size ≈ bitrate (kbps) × 1000 ÷ 8 × length (s)

AMR-NB records 8 kHz audio (300–3,400 Hz telephone band) at 4.75–12.2 kbps; AMR-WB records 16 kHz at 6.6–23.85 kbps. The ffmpeg engine decodes both and LAME encodes the MP3. Raising the sample rate adds no detail that was not recorded, but 22.05 kHz MP3 is supported by every player, while the 8 kHz variant (MPEG-2.5) is not part of the official MP3 standard and some devices refuse it.

Example

A 10-minute AMR-NB call recording at 12.2 kbps is about 0.9 MB. As a 64 kbps MP3 it becomes 64,000 ÷ 8 × 600 = 4.8 MB: larger than the AMR, and no better sounding, because the recording only holds telephone-quality speech, but it plays everywhere.