Free tool

MP3 converter

This MP3 converter turns the files on your computer or phone into MP3s inside your browser: voice memos, WAV, FLAC and AIFF files, WhatsApp voice notes and the sound of videos, at 128, 192 or 320 kbps, with nothing uploaded.

  • Free
  • Works on phones
  • Nothing is uploaded

Save as

MP3 quality

Plays everywhere. The sound is re-encoded at the quality you pick.

Choose your audio or video file

Any audio or video file, up to 1 GB and 2 hours. It’s converted in your browser; nothing is uploaded.

MP3 encoding by LAME, open-source software.

Making MP3s of lectures, calls or interviews? NoteOwl imports MP3 files on your Mac and turns them into searchable transcripts, with every speaker labelled.

Download free for MacSend to my Mac

How it works

How do you convert a file to MP3?

Choose a bitrate, then drop the file. Your browser decodes its sound, just the sound track if it is a video, and an MP3 encoder running inside the page writes a constant-bitrate MP3. Five minutes of WAV took 2.6 seconds in Chrome and 3.0 in WebKit. Listen, then download.

  1. 1

    Pick a bitrate

    128 kbps for speech, 192 kbps (the default) for most music, 320 kbps for the most faithful MP3.

  2. 2

    Choose a file on your device

    Any audio file, or a video, from your computer or phone. The converter works on files you have; it doesn’t fetch audio from website links.

  3. 3

    Save the MP3

    Play it first, then download it. The MP3 takes the original’s name with a new .mp3 ending.

How long does converting to MP3 take?

Turning audio to MP3 took two to four seconds for five minutes of sound, whatever the file was. Size depends only on bitrate and length: a 57.6 MB AIFF, a 5.11 MB FLAC and a 0.68 MB voice note each gave a 7.2 MB MP3 at 192 kbps.

WAV, 44.1 kHz stereo
Its size52.9 MB
MP3 at 192 kbps7.2 MB
Took (Chrome / WebKit)2.6 s / 3.0 s
AIFF, 48 kHz stereo
Its size57.6 MB
MP3 at 192 kbps7.2 MB
Took (Chrome / WebKit)3.1 s / 3.4 s
FLAC, 48 kHz stereo
Its size5.11 MB
MP3 at 192 kbps7.2 MB
Took (Chrome / WebKit)2.5 s / 2.8 s
M4A voice memo, AAC mono
Its size2.35 MB
MP3 at 192 kbps7.2 MB
Took (Chrome / WebKit)2.1 s / 2.6 s
OGG voice note, Opus mono
Its size0.68 MB
MP3 at 192 kbps7.2 MB
Took (Chrome / WebKit)2.3 s / 2.7 s
MP4 video, H.264 + AAC
Its size33.4 MB
MP3 at 192 kbps7.2 MB
Took (Chrome / WebKit)3.1 s / 3.6 s
WebM video, VP9 + Opus
Its size4.43 MB
MP3 at 192 kbps7.2 MB
Took (Chrome / WebKit)3.1 s / 3.7 s

What is an MP3, and why does it play everywhere?

MP3 (MPEG-1 Audio Layer III) is a compressed sound format standardised in 1993. It leaves out detail the ear is least likely to miss, so a 192 kbps MP3 is about a seventh the size of CD audio, and it plays on nearly every phone, car stereo and app.

Which bitrate should you pick for an MP3?

128 kbps for speech, 192 kbps for most music, 320 kbps for the most faithful MP3. A higher bitrate keeps more detail and takes more space, but it can’t add detail the source never had: 320 kbps won’t make a voice memo sound better than the memo itself.

128 kbps
A minute0.96 MB
An hour58 MB
SuitsLectures, meetings, podcasts, audiobooks and voice memos
192 kbps (the default)
A minute1.44 MB
An hour86 MB
SuitsMost music, and speech mixed with music
320 kbps
A minute2.4 MB
An hour144 MB
SuitsMusic from lossless FLAC, WAV or AIFF files; the highest MP3 bitrate

What sample rate and channels will the MP3 have?

The source’s own sample rate whenever MP3 can store it, which covers the usual rates from 8 to 48 kHz; 88.2 kHz becomes 44.1 and 96 kHz becomes 48. Mono stays mono, stereo stays stereo, and a file with more channels is mixed down to stereo.

Below 32 kHz, MP3 switches to its low-rate versions (MPEG-2 and 2.5), which top out at 160 or 64 kbps; the converter lowers a higher choice for you. Untick Keep the original sample rate for a 44.1 kHz MP3 at any of the three bitrates.

44.1 or 48 kHz
MP3 sample rateThe same
Highest bitrate320 kbps
32 kHz
MP3 sample rate32 kHz
Highest bitrate320 kbps
16, 22.05 or 24 kHz
MP3 sample rateThe same
Highest bitrate160 kbps
8, 11.025 or 12 kHz
MP3 sample rateThe same
Highest bitrate64 kbps
88.2 or 96 kHz
MP3 sample rate44.1 or 48 kHz
Highest bitrate320 kbps

Which files can you convert to MP3 here?

Nearly any sound file, and the sound track of most videos. Each kind below also has its own page, with the converter set up for it; this one takes them all. WMA and AMR recordings, and AVI, WMV and FLV videos, can’t be read here.

What can you do with an MP3 of a talk or a meeting?

Play it anywhere, or let NoteOwl turn it into notes. NoteOwl imports MP3 files on a Mac, transcribes them with on-device AI models, labels each speaker and keeps every transcript searchable, so an hour of talk becomes something you can find by its words.

Transcripts can be saved as Markdown, PDF or plain text. Dictation into any app is free.

FAQ

Questions about the MP3 converter

Does the MP3 converter upload my files?

No. Each file is read from your device and encoded as an MP3 inside the browser tab, then handed back for you to save; no request leaves the page during a conversion, and there is no account to make.

Why is my MP3 bigger than the original file?

Because the original used a more efficient format. Opus voice notes and AAC voice memos fit speech into very few bits: a five-minute 0.68 MB voice note became a 7.2 MB MP3 at 192 kbps, ten times larger, and 4.8 MB at 128 kbps. Pick 128 kbps for speech.

Are the MP3s constant or variable bitrate?

Constant. Every second uses the same number of bits, so sizes are predictable and identical in every browser: 0.96 MB a minute at 128 kbps, 1.44 MB at 192 and 2.4 MB at 320.

Is 320 kbps always the best choice?

Only when the source deserves it. For music from a lossless FLAC, WAV or AIFF file, 320 kbps keeps the most detail an MP3 can; keep the lossless original for archiving and editing. For speech, 128 kbps already keeps voices clear, and 320 kbps makes the file 2.5 times bigger.

What is the largest file it can convert to MP3?

Files up to 1 GB and 2 hours long. A 40-minute FLAC became an MP3 in 19.3 seconds in Chrome. Safari reads FLAC and HE-AAC files whole, so it converts those up to 30 minutes long; Chrome and Edge take them up to 2 hours.

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About NoteOwl

NoteOwl is private AI meeting notes and memory for the Mac. It captures meetings without a bot joining the call, labels every speaker, writes summaries and action items, and builds a memory of every conversation that you can chat with — fully offline, because the speech recognition and the AI run on the Mac itself. Dictation into any app is free; Pro is a one-time purchase.

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