Audio Compressor
Shrink MP3, WAV and other audio files by choosing a lower bitrate. Handy for emailing recordings, podcasts and voice notes, or fitting upload limits.
🔒 Your files never leave your device. This tool runs entirely in your web browser. Nothing is uploaded to ToolsCloset or anyone else, so it’s safe for private photos, recordings and videos.
By Shah Rukh, software developer · Last updated:
How audio compression works
The size of an MP3 depends mainly on its bitrate, measured in kilobits per second (kbps). The rough formula is:
file size (MB) ≈ bitrate (kbps) × length (seconds) ÷ 8,000
So a 4-minute song at 320 kbps is about 9.6 MB, while the same song at 96 kbps is about 2.9 MB. This tool re-encodes your audio at the bitrate you choose, and can also convert it to mono.
Which bitrate should I choose?
| Bitrate | Good for | 1 hour of audio |
|---|---|---|
| 128 kbps | Music you want to sound good | ≈ 58 MB |
| 96 kbps | Music on phones, background audio | ≈ 43 MB |
| 64 kbps | Podcasts, lectures, audiobooks | ≈ 29 MB |
| 48 kbps | Voice notes, meeting recordings | ≈ 22 MB |
| 32 kbps | Speech when size matters most | ≈ 14 MB |
Speech sounds fine at much lower bitrates than music. Choosing mono for speech keeps the voice just as clear at half the size.
Tips
- WAV files shrink the most. A WAV recording can become 10–20 times smaller as an MP3.
- Don’t compress an already-small MP3 at a higher bitrate. It won’t improve the sound and may make the file bigger.
- Want a shorter clip? Trim it first with the MP3 cutter, then compress it.
Frequently asked questions
How do I reduce the size of an MP3 file?
Lower its bitrate. Choose 96 kbps for music or 64 kbps for speech above, and tick mono for recordings of people talking.
Does compressing audio reduce quality?
A little. For speech, 48–64 kbps mono sounds almost the same as the original. For music, stay at 96–128 kbps.
Is it safe to compress private recordings here?
Yes. Everything happens in your browser, and your audio is never uploaded.
Can I compress WAV or M4A files?
Yes. Most audio formats are accepted, and the result is saved as MP3, which plays everywhere.
How long does it take?
Usually a few seconds for a song, and up to a minute or two for an hour-long recording, depending on your device.
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