Free converter · Lossy re-encode
Convert FLAC to MP3
Short answer
Drop your FLAC file into the converter below and download the MP3 file. It runs in your browser with FFmpeg, for files up to 100 MB; nothing is uploaded. The file is re-encoded to MP3 audio at about 128 kbps, keeping the source's sample rate. Re-encoding takes longer than a container swap and costs some quality; how much depends on the clip and on the quality setting, and at the converter's default setting the loss can be visible, so keep the original.
Maximum file size: 100 MB. The first conversion loads a ~30 MB converter engine, once per visit. Nothing is uploaded - conversion runs on your device.
Lossless source to lossy MP3. · Lossy re-encode · Browser-side via FFmpeg WASM - nothing uploaded.
Key takeaways
- FLAC stores the audio losslessly; MP3 is lossy, so every bit of the quality difference is permanent in the copy.
- Measured: 1,250,218 bytes of FLAC became 160,852 bytes of MP3 at 128 kbps, 87.1% smaller.
- In our test the FLAC was 65% of the size of the same audio as WAV (1,250,218 against 1,921,102 bytes).
- Keep the FLAC as your master and make MP3s from it when a device needs them.
Measured: lossless against lossy
Measured on the soundtrack of a 10 second excerpt of Big Buck Bunny (animated film; (c) Blender Foundation, CC BY 3.0), stereo, 48 kHz, using the same ffmpeg arguments this converter passes to its WebAssembly build, run with ffmpeg 6.1.1. Results describe this file.
| Format | Bytes for 10 s stereo | Bitrate |
|---|---|---|
| WAV (uncompressed) | 1,921,102 | 1,536 kbps |
| FLAC (lossless) | 1,250,218 | about 1,000 kbps |
| MP3 from the FLAC (converter default) | 160,852 | 128 kbps |
FLAC's size depends on the material; ours was a film soundtrack, which compresses less than quiet or simple recordings.
FLAC vs MP3
| FLAC | MP3 | |
|---|---|---|
| Full name | Free Lossless Audio Codec | MPEG-1 Audio Layer III |
| What is inside | Losslessly compressed audio | MP3 audio |
| Compression | Lossless | Lossy |
| Best for | Archiving music at full quality in less space than WAV | Music and podcasts that must play on every device |
What you get
MP3 audio at about 128 kbps, keeping the source's sample rate. Lossless source to lossy MP3.
Make a better MP3
ffmpeg -i in.flac -codec:a libmp3lame -qscale:a 2 out.mp3; the FFmpeg wiki says 0 to 3 normally produce transparent results.ffmpeg -i in.flac -b:a 256k out.mp3for a fixed bitrate; the wiki calls 320k generally wasteful.
Why not delete the FLAC
You cannot rebuild a FLAC from an MP3. Converting MP3 back to FLAC gives a bigger file with the same lossy sound.
Questions people ask
Is this FLAC to MP3 converter free and private?
Yes. It is free, needs no account and runs entirely in your browser, so the file never leaves your device.
Will converting FLAC to MP3 reduce quality?
Some, because MP3 is lossy and the file is re-encoded. How much depends on the clip and on the quality setting, and at the converter's default setting the loss can be visible, so keep the original. For uploads, the platform re-encodes again anyway.
Is there a file size limit?
Files up to 100 MB. The first conversion downloads a converter engine of about 30 MB once per visit; larger files are better handled by a desktop app such as HandBrake or FFmpeg.
Does FLAC to MP3 lose quality?
Yes. MP3 is lossy; the original FLAC is lossless.
How much smaller is the MP3?
In our test 87.1% smaller at 128 kbps.
Can I convert the MP3 back to FLAC?
You can, but the audio will not recover; the file will just be bigger.
What bitrate should I pick?
-q:a 2 (VBR) or 192 to 256 kbps are common choices; the FFmpeg wiki says -q:a 0 to 3 normally produce transparent results.
More converters
Sources and how we checked
- MDN: Media container formats
- MDN: Web audio codec guide
- MDN: Image file type and format guide
- FFmpeg documentation: stream copy
- FFmpeg Documentation: ffmpeg (stream selection, -map, -c copy) (read 2026-10-08)
- FFmpeg Wiki: Encode/MP3 (libmp3lame quality and bitrate) (read 2026-10-08)
- Blender Foundation: Big Buck Bunny (CC BY 3.0), the clip used for the measurements (read 2026-10-08)
Reviewed October 8, 2026. What the converter writes was measured with ffprobe on the same FFmpeg build your browser downloads; format descriptions follow MDN's media guides.