FLAC to MP3 Converter

Convert lossless FLAC audio to compressed MP3 with adjustable bitrate.

Tested tool guide Tested browser tools Checked August 16, 2026

What FLAC to MP3 Converter does, with a checked example

FLAC stores audio without losing a single sample; MP3 does not. This tool decodes a FLAC file back into raw PCM samples, then runs them through an MP3 encoder at the bitrate you choose, producing a file roughly 40 to 90 percent smaller than the source. The fact most people discover too late: the step is one-way. Everything the encoder discards is gone for good, and no later conversion can bring it back. MP3 also tops out at 320 kbps and 48 kHz, so high-resolution FLAC sources are downsampled automatically. If you may ever want a different bitrate, keep the original FLAC.

Worked example

A concrete input and expected output from the current implementation.

Input

song.flac - 44.1 kHz, 16-bit, stereo, 3 min 0 s - encode at 192 kbps CBR

Expected output

song.mp3 - 192 kbps, 44.1 kHz, stereo - about 4.1 MiB (4,320,000 bytes), compared with roughly 15 to 18 MiB for the FLAC source

A CBR MP3's size is fixed by bitrate and duration: 192,000 bits per second divided by 8 is 24,000 bytes per second, times 180 seconds is 4,320,000 bytes, about 4.1 MiB. The FLAC figure is approximate: lossless compression of 44.1 kHz stereo PCM (30.3 MiB raw) typically lands near half to three-fifths of that.

How the result is produced

Decode, then re-encode

The FLAC file is first decoded losslessly into uncompressed PCM samples; this stage is exact and returns the recording bit-for-bit. Those samples are then fed to an MP3 encoder, which applies a psychoacoustic model to judge which detail the ear could not notice, discards that detail, and packs what remains into MPEG-1 Layer III frames at the requested bitrate. All loss happens in this second stage.

Bitrate and its ceilings

You pick a constant bitrate (a fixed number such as 192 or 320 kbps) or a variable-bitrate setting that lets the encoder spend more bits on difficult passages. MP3 cannot exceed 320 kbps, and MPEG-1 Layer III frames carry only 32, 44.1, or 48 kHz sample rates (lower rates exist in MPEG-2 mode), so a 96 or 192 kHz FLAC source is downsampled to 48 kHz, and the encoder operates at 16-bit depth.

Good uses

Playing music on hardware that cannot decode FLAC: older car stereos, some portable players, and many receivers accept MP3 only.
Shrinking a library before uploading, emailing, or syncing to a phone when gigabyte-scale lossless files are impractical.
Delivering a file someone else needs in the most widely compatible format: a podcast episode, a spoken-word recording, or a rough mix sent to a collaborator.

Limits and checks

The encode is irreversible. Detail the encoder removes at the chosen bitrate is discarded permanently; converting the MP3 back to FLAC later produces a lossless wrapper around lossy audio, not the original recording.
320 kbps is a ceiling, not a promise. Two FLAC files of different quality can yield nearly identical 320 kbps MP3s, and a 96 or 192 kHz source becomes 48 kHz on output because MP3 cannot represent higher sample rates.
File size follows bitrate mechanically, so a smaller setting always discards more. Bitrate alone does not fix perceived quality either: encoder settings and source material matter, and at 320 kbps most music is audibly indistinguishable without being identical.

Common questions

Is a 320 kbps MP3 the same as a lossless FLAC?

No. MP3 is lossy at every bitrate; 320 kbps is simply the most data the format is allowed to keep. The encoder still applies its psychoacoustic model and discards detail. Most listeners cannot reliably tell 320 kbps MP3 from the FLAC in blind listening tests, but the files are not bit-identical, and the gap widens if the MP3 is ever re-encoded again.

Can I convert the MP3 back to FLAC to recover the original quality?

No. Re-encoding to FLAC preserves exactly what it is given, and what it is given is the already-lossy MP3. Everything the MP3 encoder discarded is gone. Keep the original FLAC files if you might later want a different bitrate or a different format, because that is the only copy from which a new encode starts fresh.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.