AAC to MP3 Converter
Generate the exact FFmpeg command to convert AAC audio to MP3 at any bitrate, and estimate the output file size before you run it.
File Details
Enter your file name and duration to generate the FFmpeg command and estimate the output size.
Also accepts .m4a, .mp4, or any AAC-containing file.
hrs
min
sec
FFmpeg Command Generator
ffmpeg -i input.aac -ab 192k -map_metadata 0 output.mp3
Install FFmpeg free at ffmpeg.org. Run this command in your terminal after replacing the file name.
Batch convert AAC files (Linux / macOS)
for f in *.aac; do ffmpeg -i "$f" -ab 192k -map_metadata 0 "${f%.aac}.mp3"; done
Batch convert M4A files (Linux / macOS)
for f in *.m4a; do ffmpeg -i "$f" -ab 192k -map_metadata 0 "${f%.m4a}.mp3"; done
GUI alternatives
- fre:ac — free, open-source, Windows / macOS / Linux
- Audacity — free multi-track editor; open AAC, export as MP3 (LAME required)
- VLC — free media player with built-in transcode / convert menu
- dBpoweramp — paid, fast batch conversion, Windows / macOS
Based on the duration you entered above. Formula: bitrate (kbps) × duration (s) / 8000.
128 kbps
—
192 kbps
—
320 kbps
—
96 kbps
—
256 kbps
—
Duration: 3 min 30 sec (210 s)
Why No In-Browser Conversion?
Browsers expose the Web Audio API for decoding audio, but they do not include an MP3 encoder. MP3 encoding requires the LAME library — a native binary that must be compiled for your operating system. FFmpeg bundles LAME and handles the full pipeline:
- 1 FFmpeg opens the AAC or M4A container and reads the compressed audio stream.
- 2 The AAC codec decodes the stream to raw PCM (uncompressed) audio in memory.
- 3 LAME re-encodes the PCM data to MP3 at the bitrate you specify.
- 4 FFmpeg writes the final MP3 file to disk with all metadata tags preserved.
Install FFmpeg at ffmpeg.org (free, open-source). Most Linux distributions also offer it via their package manager: sudo apt install ffmpeg or brew install ffmpeg.
MP3 Bitrate Reference
| Bitrate | Quality | Size / min | Best For |
|---|---|---|---|
| 96 kbps | Acceptable | ~0.7 MB | Voice, speech, podcasts |
| 128 kbps | Good | ~0.9 MB | Earbuds, laptop speakers |
| 192 kbps | Very Good | ~1.4 MB | General music listening |
| 256 kbps | Excellent | ~1.9 MB | Audiophile, quality headphones |
| 320 kbps | Near-lossless | ~2.4 MB | High-end systems, archival MP3 |
| VBR V0 | Transparent | ~1.5–2.5 MB | Best quality-to-size ratio |
AAC vs. MP3 — At a Glance
AAC (Advanced Audio Coding)
- Better quality than MP3 at the same bitrate
- Default format for Apple, YouTube, and most streaming platforms
- Supports up to 48 audio channels
- Not universally supported by older hardware and software
- Cannot be encoded natively by browsers or basic editors
MP3 (MPEG-1 Audio Layer III)
- Universally compatible with every device and platform
- Supported by car stereos, older players, and all software
- Widely supported for podcast and audio distribution
- Lower quality than AAC at equivalent bitrates
- Discards audio data permanently (lossy)
Summary
Generate the exact FFmpeg command to convert AAC audio to MP3 at any bitrate, and estimate the output file size before you run it.
How it works
- Enter your AAC file name and its duration in the form below.
- Choose a target MP3 bitrate — 128 kbps for casual listening, 192 kbps for general use, 320 kbps for the highest quality.
- Copy the generated FFmpeg command.
- Open a terminal, paste the command, and run it. FFmpeg decodes the AAC and re-encodes to MP3 using the LAME encoder.
- Play the output MP3 to verify quality before deleting your original AAC file.
Use cases
- Convert Apple Music downloads or iTunes purchases from AAC to universally compatible MP3.
- Prepare audio tracks for devices or software that do not support AAC (some car stereos, older players).
- Strip AAC audio from an M4A or MP4 container and re-encode as MP3 for podcast distribution.
- Batch-convert an entire AAC music library to MP3 using a shell loop.
- Estimate the output MP3 file size before committing to a large batch conversion.
- Generate a ready-to-paste FFmpeg command without memorizing its flags.
- Compare AAC and MP3 quality characteristics before choosing a target bitrate.
- Convert audiobooks or spoken-word AAC files to MP3 at a lower bitrate to save space.