FLAC: lossless, but big
FLAC stands for Free Lossless Audio Codec. Josh Coalson released it in 2001 and it is now maintained by the Xiph.Org Foundation. It compresses audio the way a zip file compresses text: the decoded result is bit-for-bit identical to the original.
CD-quality FLAC (16-bit, 44.1 kHz stereo) usually lands at 50 to 70% of the WAV size, roughly 5 to 7 MB per minute. Hi-res FLAC at 24-bit and 96 kHz is much larger. Music stores that sell lossless downloads and people who rip CDs carefully tend to use FLAC.
MP3: small and everywhere
MP3 is a lossy format from Fraunhofer IIS and the MPEG group, standardised in 1993. It uses a psychoacoustic model to throw away detail you are unlikely to hear. At 320 kbps a minute of stereo takes about 2.4 MB; at 192 kbps, about 1.44 MB. It handles sample rates up to 48 kHz.
The reason to convert FLAC to MP3 is compatibility and space. Many car stereos, older iPods, basic Bluetooth speakers and some DJ and fitness apps only take MP3. Apple Music and iTunes on the Mac do not import FLAC either.
FLAC vs MP3 compared
| FLAC | MP3 | |
|---|---|---|
| Compression | Lossless | Lossy |
| Quality | Identical to the source | Very close at 256 to 320 kbps |
| Bit depth / sample rate | 16 or 24-bit, up to 192 kHz is common | Not bit-depth based; up to 48 kHz |
| Typical size per minute | About 5 to 7 MB (CD quality) | About 2.4 MB at 320 kbps, 1.44 MB at 192 kbps |
| Compatibility | Good on Android and desktop players; limited in Apple Music | Near universal |
| Best for | Archiving and critical listening | Portable players, cars, sharing |
How much quality do you lose?
Going from FLAC to MP3 is lossless to lossy, so some information is discarded. The good news is that FLAC is the ideal starting point. The MP3 encoder sees the full original signal, so the only loss is the one MP3 itself introduces.
At 320 kbps most listeners cannot tell a well-encoded MP3 from the FLAC in normal listening. At 192 kbps the difference is small on most music. Below that, cymbals, reverb tails and dense mixes begin to show artefacts.
Keep your FLAC files. If you ever need a different bitrate or format, encode again from the FLAC rather than from an MP3, which would stack a second round of loss on top of the first.
Picking a bitrate for FLAC to MP3
Think about where the files will be played, then pick the lowest bitrate that still sounds right to you.
- 320 kbps: the best MP3 can do. Use it for music you care about.
- 256 kbps: very close to 320 and about 20% smaller.
- 192 kbps (default): a good balance for large libraries on a phone.
- 128 kbps: audiobooks, spoken word, or when space is very tight.
Hi-res FLAC and other details
Hi-res FLAC files at 24-bit and 88.2, 96 or 192 kHz carry more data than any MP3 can hold. MP3 has no bit depth setting in the way PCM does, and the format tops out at a 48 kHz sample rate. For listening on a phone or in a car, a 320 kbps MP3 made from hi-res FLAC still sounds excellent, but the hi-res part of the file does not survive the trip.
Gapless albums are another thing to know about. MP3 encoders add a tiny amount of padding at the start and end of each track. Most modern players hide it, but some older players may leave a short gap between tracks on live albums or continuous mixes.
Finally, file names carry over but tags may not. If your player sorts by artist and album, give the MP3s a quick check after you convert.
Why it is safe to convert your library here
Albums can be large, and uploading hundreds of megabytes to a web converter is slow. AudioDrop does not upload anything. Your browser decodes the FLAC and a LAME-based encoder compiled to WebAssembly writes the MP3, all on your own computer or phone.
Drop a full album and the tracks convert in parallel, each downloading separately. Once the page is loaded it keeps working offline. There is no file size cap beyond your device's memory. Tags such as artist, album and cover art are not guaranteed to carry over, so check them in your music app afterwards.