Convert FLAC to MP3

The one transcode with a clean source

FLAC is lossless — it compresses sound the way a ZIP compresses a document, so what comes out is bit for bit what went in. That makes this the best case for any conversion to MP3, and it is genuinely different from converting an AAC or an OGG. There is no earlier generation of damage for the encoder to waste bits on and no two codecs disagreeing about what is inaudible: this is one clean pass from a perfect source, which is exactly what MP3 was designed for and where it performs at its best.

That means the bitrate you pick is the only thing that matters, and you can trust it. 320 kbps is as much as MP3 offers and is indistinguishable from the FLAC for nearly everyone on nearly all material. 192 is the sensible default for music going onto a phone — a tenth of the FLAC's size, and honest listening tests put it past the point most people can reliably tell apart. 128 is fine for speech and audiobooks and audibly thin on cymbals and applause.

Keep the FLAC. This is the one piece of advice worth more than the rest of this page: the MP3 is a delivery copy, and the FLAC is the master. If you later want a different bitrate, a different format, or whatever replaces MP3 next, you convert again from the lossless original and lose nothing. Delete the FLAC and every future conversion starts from something already damaged.

Two of FLAC's capabilities do not fit through MP3 and are quietly folded away. FLAC holds up to eight channels, so a surround recording comes back as stereo, and it holds 24-bit audio at 96 or 192 kHz, where MP3 stops at 48 kHz — a high-resolution download is resampled on the way through. Neither is audible on ordinary listening equipment, and both are real. Tags and cover art are not carried across yet.

When you want something else

For a library, ffmpeg keeps the tags and artwork that make the files usable: ffmpeg -i in.flac -c:a libmp3lame -q:a 0 -map_metadata 0 out.mp3. -q:a 0 is variable-bitrate encoding at the top quality setting, which averages around 245 kbps and is generally preferred over fixed 320 — it spends bits on the difficult passages instead of spreading them evenly. foobar2000 and fre:ac do the same with a front end and handle thousands of files.

If the destination can take something newer, MP3 is no longer the best answer to this question. Opus at 128 kbps beats MP3 at 256, and AAC beats it at every bitrate — both are played by every current phone and computer. MP3 is the right choice specifically when an older device is involved, and the wrong one when nothing in the chain requires it.