How do I convert MP3 to FLAC?

Converting MP3 to FLAC wraps your decoded audio in a lossless container — but the result is only as good as the MP3 that went in. FLAC encoding is mathematically lossless from its input, and its input here is the decoded MP3: every artefact and every missing frequency of the original lossy encode is preserved exactly. No detail is recovered. This is the single most misunderstood conversion in audio; see lossy vs lossless explained.

There are legitimate reasons to do it. Some archival systems, editors, and players standardise on FLAC intake. FLAC guarantees zero further loss through any number of future format migrations, has robust checksummed integrity verification, and carries richer tagging. Converting a collection to a uniform FLAC library "freezes" the current quality permanently — nothing gets worse from here, no matter how many times the files are moved, retagged, or converted onward losslessly.

Expect the file to grow: FLAC compresses the decoded PCM, and PCM from a 128 kbps MP3 is the same size as PCM from a studio master. A 4 MB MP3 typically becomes a 20–30 MB FLAC. One etiquette note: never share MP3-sourced FLAC as if it were true lossless — communities call these "transcodes" and spectral analysis exposes them instantly (MP3's lowpass cutoff is visible around 16–20 kHz).

Reasons to convert MP3 to FLAC usually come down to compatibility, file-size, or specific feature requirements. Common situations:

• An app or platform only accepts FLAC uploads.
• You need a feature unique to FLAC (e.g. lossless editing, chapter markers, smaller streaming size, etc.) that MP3 doesn't provide.
• You're optimising file size — modern formats often produce smaller files than the older format you started with.
• You need a single archival format across a project so files behave consistently in the same viewer.

1. Open the MP3 → FLAC tool on mp3.now.
2. Drag your MP3 file onto the drop zone, or click Select files. You can drop a whole folder of files at once.
3. The output is fixed to FLAC. If the format supports extra options (bitrate, sample rate, channels, volume normalization), tweak them in the options panel.
4. Click Convert. The job runs on our server and finishes in a few seconds for typical tracks.
5. Download the result. Files stay in storage for 24 hours and are then permanently deleted.

The entire flow is free for the first 10 jobs per day with no signup required. A free account doubles that quota; a premium plan removes the limit entirely.

• A FLAC made from an MP3 sounds exactly like the MP3 — lossless from here on, but the past loss is baked in.
• Label MP3-sourced FLACs honestly; don't present them as true lossless rips.
• Expect 5–8× size growth over the source MP3.
• Use this to freeze quality before a long chain of future edits or migrations.
• If you own the CD or original master, rip that to FLAC instead — it's the real thing.