Compress audio files

How audio compression works

MP3 file size is set by the bitrate, the number of kilobits used for each second of sound. A lower bitrate tells the encoder to use fewer bits, which makes a smaller file. The cost is some high-frequency detail and, at very low bitrates, a slightly swirly sound on music.

How to compress an audio file

Drop an MP3, WAV, FLAC, M4A, AAC, OGG, Opus, WebM or AMR file above. Pick a bitrate from the grid: 320, 256, 192, 160, 128, 96, 64, 48 or 32 kbps. Press Compress audio and the file is re-encoded as an MP3 at exactly that bitrate in your browser. The result shows the new size so you can check it against your limit before you download.

Which bitrate should I pick?

Pick by what is in the file:

• 192 or 160 kbps for music that should sound close to the original.
• 128 kbps for music when size matters, a good balance for most listening.
• 96 or 64 kbps for podcasts, lectures and interviews.
• 48 or 32 kbps for voice notes and long recordings where small size matters most.

Estimate the compressed file size

MP3 size depends only on bitrate and length. One minute of audio takes about 2.4 MB at 320 kbps, 1.4 MB at 192 kbps, 1 MB at 128 kbps, 0.5 MB at 64 kbps and 0.24 MB at 32 kbps. A one-hour podcast at 64 kbps is about 29 MB. Choosing a bitrate above the source bitrate makes the file bigger without improving it.

Before you start

Input: MP3, WAV, FLAC, M4A, AAC, OGG, OPUS, WEBM, and AMR. Output: MP3. The settings appear before anything runs, so you can check them first. Your original file is never changed.

Converting audio can change the codec, bitrate, channels, tags and length. Listen to the start and end of the result. Keep a lossless original if you may edit it again.

Keep the original until you have opened and checked the result. The work happens in this browser tab, so the size you can handle depends on your device's memory, your browser and the file itself.

How to compress audio files

1. Drop an audio file into the zone above.
2. Choose a target bitrate. Lower means a smaller file.
3. Press Compress audio, then download the smaller MP3.