How to Convert Video to MP3 on Linux

Short answer: run ffmpeg -i input.mp4 -vn -c:a libmp3lame -b:a 192k output.mp3. That strips the video, keeps the audio, and gives you an MP3 that plays on anything. I tested this on a 60-second clip on October 28, 2026: the 192k MP3 came out at 1.44 MB (down from a 21.1 MB video), the conversion took under a second, and the 60 seconds of audio survived intact. If you don't care about the MP3 format specifically, there is an even faster trick below that skips re-encoding entirely.

Why convert video to MP3 at all?

People usually want this for one of a few reasons: keeping the audio from a lecture, podcast, or music video to listen to on the go; shrinking a file before sending it; or getting audio into a tool that only accepts MP3. A video file is mostly video data — in my test clip, the picture was about 20 MB of the 21.1 MB total. Throw the picture away and the file collapses, because audio needs far less data than moving images.

One thing to be clear about up front: only convert videos you own or have permission to use.

How I tested

I generated a 60-second 1280×720 test clip with FFmpeg itself — a moving test pattern with a steady 440 Hz tone as the soundtrack — and encoded it as an MP4 with H.264 video and 192k AAC audio. That gave me a known, repeatable "original": 21,080,259 bytes (21.1 MB), exactly 60 seconds long. Then I converted that same file five ways: MP3 at 128k, MP3 at 192k, MP3 at 320k, copying the original audio without re-encoding (as M4A), and uncompressed WAV for comparison.

For each output I recorded the file size, the conversion time, and the duration (checked with ffprobe) to make sure nothing was cut off. Test environment: FFmpeg 8.1.2 on Ubuntu 24.04, a 2-vCPU machine. The audio here is a simple tone, so these results measure size and speed precisely; they are not a listening test of music quality, and I won't pretend otherwise.

The results

Three things stand out:

1. The bitrate math checks out. MP3 size is almost entirely decided by the bitrate you choose: 128 kilobits per second × 60 seconds ÷ 8 bits per byte = 960,000 bytes, and my actual file was 961,035 bytes — the tiny extra is just metadata tags. Double the bitrate to 320k and the file is 2.5× bigger (2.40 MB vs 0.96 MB). You can predict the size of any conversion before you run it.

2. The no-re-encode trick is the fastest option by far. Copying the original AAC audio stream into an M4A file took 0.09 seconds — roughly eight times faster than re-encoding to MP3 — and it loses zero quality, because the audio is never decoded and re-encoded. The only catch is that you get an M4A file instead of an MP3. That plays fine on modern phones, browsers, and media players, but if you specifically need the .mp3 extension (an old car stereo, for example), use the real MP3 conversion instead.

3. Every conversion took under a second for a 60-second clip. Audio encoding is cheap. Even on this modest 2-vCPU machine, converting a full hour of video to MP3 should take roughly a minute — so pick your setting based on size and compatibility, not speed.

The exact commands

Install FFmpeg first (sudo apt install ffmpeg on Ubuntu/Debian, or see ffmpeg.org for other systems). Then, from the folder containing your video:

The everyday conversion (my recommendation):

ffmpeg -i input.mp4 -vn -c:a libmp3lame -b:a 192k output.mp3

What the flags mean: -vn drops the video stream, -c:a libmp3lame selects the MP3 encoder, and -b:a 192k sets the audio bitrate. Change input.mp4 and output.mp3 to your own filenames.

Smallest good-enough MP3:

ffmpeg -i input.mp4 -vn -c:a libmp3lame -b:a 128k output.mp3

Fastest option, zero quality loss (gives you M4A, not MP3):

ffmpeg -i input.mp4 -vn -c:a copy output.m4a

This only works if the video's audio is already AAC, which is true for most MP4 files from phones and cameras. If FFmpeg complains, fall back to the MP3 command above.

Convert a whole folder at once:

for f in *.mp4; do ffmpeg -i "$f" -vn -c:a libmp3lame -b:a 192k "${f%.mp4}.mp3"; done

I ran exactly this loop on two copies of my test clip and both came out at 1,441,479 bytes with the full 60 seconds intact. The "${f%.mp4}.mp3" part just swaps the extension, so lecture.mp4 becomes lecture.mp3.

Uncompressed audio for editing: ffmpeg -i input.mp4 -vn -c:a pcm_s16le output.wav — my WAV was 5.29 MB, about 5.5× the 128k MP3, but it throws nothing away, so it is the best starting point for editing.

Which bitrate should you pick?

• 128k: Spoken word — lectures, podcasts, interviews. Voices sound fine, and the file stays tiny.
• 192k: The all-rounder, and my default. Music sounds good, the file is still small (about 1.4 MB per minute), and it plays everywhere.
• 320k: Music you care about and have storage for. It is 2.5× the size of 128k, and on most everyday listening gear the difference over 192k is hard to hear.

One rule that applies to all of these: never convert MP3 back to a "higher quality" format and expect it to sound better. Once audio has been compressed to MP3, the discarded detail is gone for good. Converting that MP3 to WAV or 320k just makes a bigger file of the same sound. Always convert from the original video, not from an MP3 you made earlier.

FAQ

Will the MP3 sound worse than the original video's audio? At 192k or 320k, the difference is very hard to hear for most material. MP3 is lossy — it discards some audio information — but at these bitrates it discards the parts human hearing notices least. The FFmpeg MP3 encoding guide explains the settings, and the LAME project (whose encoder FFmpeg uses) documents the trade-offs. At 128k, trained ears can hear artifacts in complex music, but speech is unaffected.

Does this work on videos from my phone? Yes. Phone recordings are MP4 (or MOV) files with H.264/H.265 video and AAC audio — the same commands apply. Copy the file to your computer first, or run FFmpeg on the phone itself if you have a terminal app.

Why is my converted MP3 bigger than expected? Check the bitrate you actually used — if you leave out -b:a, FFmpeg uses variable bitrate, which can land anywhere depending on the content. Setting -b:a explicitly gives you the predictable sizes in the table above.

Can I convert back from MP3 to video? You can put MP3 audio into a video container, but you can't recover the picture — it was discarded. If you might want the video later, keep the original file and treat the MP3 as a copy, not a replacement.

Conclusion

Converting video to MP3 on Linux is one command, and the test results leave little room for doubt: ffmpeg -i input.mp4 -vn -c:a libmp3lame -b:a 192k output.mp3 turns a 21.1 MB video into a 1.44 MB MP3 in under a second, with all 60 seconds of audio intact. If you don't specifically need the MP3 format, the -c:a copy shortcut is even faster and loses nothing at all. Pick 128k for speech, 192k for everything else, 320k for music you want to keep at the best MP3 quality — and always convert from the original.

How this article was made

Test clip generated October 28, 2026, with ffmpeg -f lavfi -i "testsrc2=size=1280x720:rate=30:duration=60" plus a 440 Hz sine tone, encoded as H.264 video with 192k AAC audio (21,080,259 bytes, 60.00 s). All five conversions ran on the same Ubuntu 24.04 machine (2 vCPUs) with FFmpeg 8.1.2; durations verified with ffprobe, and the batch loop was run on two copies of the clip. All three external links were checked to return HTTP 200 on October 28, 2026. Note that the audio in this test was a simple tone, so the size and speed figures are exact but this was not a music listening test. This article was drafted with AI assistance; every number, timing, and command result comes from the author's own test runs on that date.