FLAC vs MP3

FLAC keeps every bit of the recording; MP3 keeps what you’re likely to hear. The question is whether you can hear what MP3 drops, and the answer depends on the bitrate.

	FLAC	MP3
Compression	Lossless (like ZIP)	Lossy (psychoacoustic)
Size per minute	≈ 5–6 MB	0.96 MB (128k) – 2.4 MB (320k)
Frequency range	Full (to 22 kHz at 44.1 kHz)	Cut at ≈ 16–20 kHz depending on bitrate
Re-encoding	No loss, ever	Loses a little each time
Plays on	Android, Windows, macOS, iOS (Files), hi-fi players	Everything
Best for	Archiving, editing sources, hi-fi	Phones, cars, sharing

The part you can actually test: the high-frequency cutoff

To stay within its bitrate budget, an MP3 encoder first filters off the highest frequencies, where most adults hear little. The LAME encoder cuts at about 17 kHz for 128 kbps and 19–20 kHz at 192–320 kbps. FLAC keeps everything up to half the sample rate.

Play the test sound and switch between formats. If you can’t hear a change between FLAC and 192 kbps, a 192 kbps MP3 is transparent for your ears on that equipment, at least as far as bandwidth goes.

Beyond the cutoff

Bandwidth isn’t the whole story. Low-bitrate MP3s also show pre-echo (a smear before sharp hits like castanets), a swishy “underwater” texture on cymbals and applause, and a narrower stereo image because of joint-stereo coding. These artefacts are what trained listeners pick out in ABX tests; at 256–320 kbps they are very hard to hear.

Converting between them

FLAC to MP3: choose 320 kbps for the best MP3 you can make from a lossless file.
MP3 to FLAC: only when an app requires FLAC; it won’t restore quality.
FLAC to WAV and WAV to FLAC: lossless both ways.

Questions people ask

Is FLAC better than MP3?

FLAC is lossless: it reproduces the original recording exactly. MP3 discards detail to save space. Whether you can hear the difference depends on the bitrate, your ears and your equipment. At 320 kbps most people can’t in blind tests; at 128 kbps many can on good headphones.

How much bigger is FLAC than MP3?

CD-quality FLAC is roughly 5–6 MB per minute, about 2.5–3× a 320 kbps MP3 and 5–6× a 128 kbps MP3. An album is typically 250–400 MB in FLAC versus 60–150 MB in MP3.

Does converting MP3 to FLAC improve quality?

No. FLAC stores exactly what it is given, so an MP3 converted to FLAC sounds identical to the MP3 and is much larger. Only rip or buy FLAC from a lossless source.

Can Bluetooth headphones play FLAC quality?

Not fully. Bluetooth codecs (SBC, AAC, aptX, LDAC) re-compress audio before sending it. LDAC at 990 kbps comes closest. On standard Bluetooth, a 256 kbps AAC file and a FLAC sound the same.

Which should I use?

Keep FLAC for your archive: CD rips, purchased hi-res files, your own recordings. Convert to MP3 or AAC for phones, cars and sharing. You can always make a new MP3 from FLAC, never the other way round.