FLAC or MP3: Which Should You Choose?

FLAC: smaller file, same samples

FLAC packs audio samples so decoding brings back exactly the same values. No missing detail. That refers to the audio data: WAV headers and extra metadata need not be identical byte for byte. File size depends on the recording and compression settings. A higher compression level may save space at the cost of encoding time; it is not a secret “make it sound better” button.

MP3: travelling light comes with a trade-off

MP3 goes for a smaller file using lossy compression. The encoder creates a more compact representation, and the decoder cannot recover every original sample. Bitrate, measured in kilobits per second, affects size and potential quality. Will you hear the difference? That depends on the material, encoder, listener and listening conditions. A “320 kb/s” label is not a certificate of excellent ancestry.

Leave sample rate and musical tuning alone when comparing these formats. Raising 44.1 kHz to 96 kHz cannot recreate information that was never there. The bigger number looks impressive, but it cannot travel back in time.

Let us try it: 30 seconds, four files

Rather than guess, we made a short example of our own: a synthetic melody with a low tone, without using anyone else’s recordings. The source is 30 seconds of stereo, 44,100 Hz, 16-bit PCM audio. We encoded the same WAV to FLAC and constant-bitrate MP3 at 192 and 320 kb/s, using FFmpeg and libmp3lame. Volume, tuning and sample rate stayed put.

Here, 1 MB means 1,000,000 bytes. Sizes cover the complete files, headers included. These are results for these particular samples, not a promise that your entire music collection will shrink by the same amount. A simple signal can compress differently from acoustic music.

We decoded the FLAC to 16-bit PCM and compared its samples with the WAV: exactly the same audio bytes. This conversion is lossless. It does not tell us how the MP3 sounds, and it is not a benchmark of Perun Audio Converter. We are checking our example files here.

If your browser refuses to play FLAC, download it from the table and use a compatible player. Keep playback volume the same: louder is very good at pretending to be better. Cannot hear a difference? That is fine. This short sample does not settle the question for every other recording.

Measurement data: file sizes, FFmpeg version and PCM SHA-256 checksum

Make an MP3 from FLAC, step by step

1. Keep the source FLAC in a separate folder or backup.
2. Open it in a converter that supports FLAC input and MP3 output.
3. Select MP3 and start with 192 kb/s. If retaining detail matters more than size, compare 320 kb/s as well.
4. Keep the source sample rate and channel count. Disable extra effects and tuning changes.
5. Save to a new file. Check the beginning, ending, duration and track information, then play it on the target device.

For supported formats and settings in our application, see Perun Audio Converter. Match your settings to the task: a straightforward format conversion does not require changing musical tuning.

MP3 to FLAC: does the quality come back?

No. FLAC preserves the decoded MP3 audio losslessly, including its limitations. It cannot recover information discarded by the earlier encoder. It can still be a useful working file, avoiding more lossy saves during editing, but it cannot replace the original from before compression. Bigger suitcase, same contents.

Phone, archive or editing: what fits the job?

• Archive: retain the original. For PCM sources, FLAC provides lossless storage and can be smaller than uncompressed PCM, depending on the material.
• Phone with limited storage: make MP3 copies and compare settings using your own tracks.
• Older equipment: check the device manual for supported formats, bitrates and sample rates.
• Editing: work from a lossless source and export MP3 at the end, rather than repeatedly encoding MP3 to MP3.

Technical sources

Xiph.Org: FLAC features · Library of Congress: MP3. The table and listening samples are our own MIERZWA Studio example.