AudioKit

MP3 compressor

Make an MP3 smaller by lowering its bitrate: pick a size it has to fit, a percentage of the original, or a preset for voice or music.

  • Runs on your device
  • No upload
  • No sign-up
  • Free

Drop a MP3 file to compress

Stays on this device: nothing is uploaded. You can also drag a file here or paste it.

How MP3 compression works

An MP3’s size is its bitrate multiplied by its length, so the only real way to make an MP3 smaller is to re-encode it at a lower bitrate. A 5-minute song at 320 kbps is about 12 MB; at 128 kbps it’s about 4.8 MB.

Check the “average kbps” shown after you open the file. If it already says 128, compressing to 96 kbps saves 25%; going below 64 kbps makes music sound noticeably thin. For speech, mono at 48–64 kbps stays perfectly clear.

MP3 re-encoding is lossy each time, so always compress from the best copy you have, not from a file you already compressed.

Other compressors: WAV compressor · M4A compressor · any audio format. To understand the numbers, see what bitrate means.

Audio file size calculator

≈ 4.8 MB (192 kbps × 210 s ÷ 8)

Questions people ask

How do I reduce an MP3 file size without losing quality?

You can’t shrink an MP3 with zero loss, because the size comes from its bitrate. You can make the loss inaudible: going from 320 to 192 kbps saves 40% and very few listeners can tell. For voice, switching to mono saves half with no audible change.

How do I compress an MP3 to a specific size?

Choose “To a target size” and type the size in MB. AudioKit divides the size by the length to find the highest bitrate that fits, leaving 4% for headers.

Can I compress several MP3 files?

This tool handles one file at a time. To shrink a batch to the same bitrate, use the converter on the home page, pick MP3 and a lower bitrate, and drop all the files at once.

What is the smallest usable MP3 bitrate?

About 32 kbps mono for speech (it sounds like a phone call). For music, 96 kbps is roughly the lowest that still sounds acceptable. If you need smaller than that, Opus at 32–48 kbps sounds far better than MP3.

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