How to Convert MP4 to MP3 and Pick the Right Bitrate

Converting MP4 to MP3 means taking the audio track out of a video and saving it as a standalone audio file; the picture is thrown away. Because video takes up most of an MP4's size, the MP3 is a small fraction of the original — and it plays on every phone, car stereo and media player.

The quickest way is our video to MP3 converter: upload the MP4, download the MP3, nothing to install. This guide is about MP4 files specifically — quality, bitrate, large files, and doing it on Windows, Mac and iPhone. For other video formats and for saving audio in formats other than MP3, see how to extract audio from video.

What Happens When You Convert MP4 to MP3

An MP4 is a container. Inside there's usually a video stream (H.264 or HEVC) and an audio stream (usually AAC). When you convert to MP3, the audio stream is decoded and re-encoded as MP3, and the video stream is dropped.

That's why the file shrinks so much: the MP3 carries only the sound. Its size depends only on bitrate and length — about 1.4 MB per minute at 192 kbps — no matter how big the video was.

One caveat: conversion can't improve sound. If the video was recorded with a poor microphone, the MP3 will sound the same or slightly worse, never better.

Best Bitrate for MP4 to MP3

Bitrate sets the balance between quality and size. The sizes below are arithmetic (bitrate × 30 minutes):

For music, around 192 kbps is the sensible default. For talks, lectures and podcasts, 128 kbps is plenty — speech doesn't need the headroom that music does.

Going above the bitrate of the original audio track adds size, not quality: a video with 128 kbps AAC audio won't sound better as a 320 kbps MP3.

How to Convert MP4 to MP3

Convert MP4 to MP3 Online (No Install)

1. Open the video to MP3 converter
2. Drag in your MP4 (or MOV, AVI, MKV, WMV, FLV, WebM) — up to 20 files at once
3. Click Convert — there's no setting to choose
4. Download the MP3, or all of them as one ZIP

The converter encodes a high-quality variable-bitrate MP3 averaging around 190 kbps. It works from Safari on iPhone, Chrome on Android, and any desktop browser; the conversion runs on our servers. Need a smaller file for speech? Run the MP3 through the audio compressor and pick 64–128 kbps.

Convert MP4 to MP3 on Windows and Mac with VLC

VLC is free and open source on Windows, Mac and Linux:

1. Open VLC → Media → Convert/Save (Ctrl+R)
2. Click Add, choose your MP4 file(s), then Convert/Save
3. In the Profile dropdown, choose Audio - MP3
4. Set the destination file and click Start

Add several files in step 2 and VLC converts them one after another.

Convert MP4 to MP3 on iPhone

iOS has no built-in way to save a video's sound as MP3. In Safari, open the video to MP3 converter, tap the upload area, pick the video from Photos or Files, and save the MP3 to the Files app when it's ready. Screen recordings and videos from the Camera app are MP4 or MOV — both work.

Convert MP4 to MP3 with FFmpeg (Command Line)

FFmpeg is the free command-line tool behind many converters. To pull the audio out as MP3 at 192 kbps:

ffmpeg -i video.mp4 -vn -codec:a libmp3lame -b:a 192k audio.mp3

-vn drops the video; -b:a sets the bitrate. For a whole folder on macOS or Linux:

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

Convert MP4 to MP3 in Python (MoviePy)

For scripts that already use Python, MoviePy wraps FFmpeg:

from pathlib import Path
from moviepy import VideoFileClip

for path in Path("videos").glob("*.mp4"):
    with VideoFileClip(str(path)) as clip:
        clip.audio.write_audiofile(str(path.with_suffix(".mp3")), bitrate="192k")

Install it with pip install moviepy. The import above is for MoviePy 2; in version 1 it's from moviepy.editor import VideoFileClip. Set bitrate explicitly — otherwise the MP3 gets the encoder's default.

Convert Large MP4 Files to MP3

Long lectures, recorded meetings and full films are often 500 MB or more.

• Online: the upload limit is 100 MB as a guest, 500 MB on Premium and 1 GB on Premium Plus. Within the limit, the upload usually takes longer than the conversion — at 50 Mbps, a 1 GB file needs about 3 minutes just to upload.
• Over the limit or on a slow connection: convert locally with VLC or FFmpeg. Nothing is uploaded, and the output is the same MP3.
• Output size: a 1-hour MP3 is about 58 MB at 128 kbps and 86 MB at 192 kbps, whatever the size of the video.

Converting M4A (MPEG-4 Audio) Files

Files labelled "MP4A", "MPEG-4 Audio" or ending in .m4a are MP4 containers with audio only — usually AAC. Voice Memos on iPhone and GarageBand exports are typical sources.

They aren't videos, so use the M4A to MP3 converter instead of the video one. The M4A to MP3 guide covers them in detail.

Troubleshooting MP4 to MP3 Conversion

The Converter Says There's No Audio

Some MP4s have no audio track at all — screen recordings with sound off, or GIFs saved as MP4. Open the file in VLC: if the Audio → Audio Track menu is empty or greyed out, there's nothing to extract.

The File Is Rejected as Protected

Videos bought or rented from stores such as iTunes are DRM-protected. Their audio can't be converted, online or with VLC.

The MP3 Is Bigger Than Expected

Check the bitrate the desktop tool used and the length of the recording: a 2-hour MP3 at 320 kbps is about 288 MB. For speech, 128 kbps sounds nearly the same at 40% of that size.

Summary

Extracting the audio from an MP4 is quick, and at around 192 kbps music keeps its quality while the file becomes a fraction of the video's size. Use the video to MP3 converter for single files or up to 20 at once, and VLC or FFmpeg for big files and whole folders.

Related Tools

• Extract audio from video — other video formats and audio targets
• M4A to MP3 — Apple audio files from Voice Memos and iTunes
• WAV to MP3 — uncompressed audio from recorders
• FLAC to MP3 — lossless music files
• Video to MP3 converter — MP4, MOV, AVI, MKV, WMV, FLV and WebM