Convert MP4 to MP3 at 320 kbps

How to Convert to MP3

1. 1

   Add your MP4 file

   Up to 300 MB, including the .m4v files iTunes and some cameras produce. The picture is never decoded, so the limit here is much higher than for tools that touch every frame.

2. 2

   Pick an MP3 bitrate

   192 kbps is plenty for the AAC track inside a typical MP4; 128 keeps a lecture small, and 320 only pays off when the source audio was high quality to begin with.

3. 3

   Click Convert and download

   The MP3 keeps the video's file name and length and weighs roughly 1.4 MB per minute at 192 kbps.

Every MP3 frame at 320 kbps

The page opens with “320 kbps” selected in the row of three bitrates. Under “More settings”, “Sample rate” and “Channels” stay on “Keep original”, and “Loudness” stays “Off”. A 48 kHz stereo track therefore becomes a 48 kHz stereo MP3. The bitrate is constant: in our check on October 21, 2026, all 1,252 MP3 frames of a 30-second result were 320 kbps. That is 2.4 million bytes a minute. The result card counts a megabyte as 1,048,576 bytes and showed those 30 seconds as 1.1 MB, or 704 kB at 192. The MP3 keeps the video's name: holiday.mp4 becomes holiday.mp3.

A 128 kbps track gains nothing at 320

The MP3 is made from the sound track stored inside the MP4, so it cannot hold more than that track. Our 30-second test clip carried synthesized music, encoded at 128 kbps by Apple's AAC encoder. That track stopped at about 18 kHz: from 18 to 19 kHz it was 30 dB below the original, and higher up 58 dB or more. The 320 kbps MP3 stopped at the same 18 kHz, and so did the 192 kbps one. We also subtracted each file from the original recording and measured the remainder. For the 320 kbps MP3 it was as loud as for the AAC track, about 14.5 dB below the music. The MP3 copied the track, gaps included, at 2.5 times the track's size. We ran no listening test.

Where 320 keeps more than 192

The same music encoded at 256 kbps kept the original up to about 22 kHz. From that track, the 192 kbps MP3 dropped everything above about 19 kHz. The 320 kbps one kept the sound up to about 20.5 kHz, the ceiling of the page's MP3 encoder at that rate. Its remainder was 17.6 dB below the music, against 15.5 dB at 192 and 19.5 dB for the AAC track itself. So 320 stayed closer to the original than 192, though not as close as its source. In our test, 320 paid for its size on the 256 kbps track and only added bytes on the 128 kbps one.

Long recordings, and the AAC kept as it is

The page takes an MP4 or M4V of up to 300 MB and one hour. The sound is decoded and encoded in the browser tab, so the video is not uploaded. In Chrome on a 2023 Mac, our clip took under three seconds the first time, most of it downloading the converter, about 10 MB. A second file in the same tab took half a second. A 59-minute file took 22 seconds, and its 135 MB MP3 outweighed the 70 MB MP4, whose picture ran at one frame a second. A 61-minute file was refused, with its length given in seconds. If your player takes AAC, Audio from Video set to AAC copies the track without re-encoding. Our 128 kbps clip gave a 479 kB file with the same audio data as the video, byte for byte.

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