AudioKit

Compress audio and MP3 files

Make an audio file small enough for email, Discord or WhatsApp. Pick a purpose, or type the size it must fit, and AudioKit works out the bitrate.

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

Drop an audio file (or a video) to shrink

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

How audio compression shrinks a file

An audio file’s size is almost exactly its bitrate × duration. A 4-minute song at 320 kbps is 320,000 bits × 240 seconds ÷ 8 ≈ 9.6 MB. At 128 kbps it’s 3.8 MB. That’s all “compress audio” really does: re-encode at a lower bitrate, and optionally mono and a lower sample rate for speech.

Which bitrate you can get away with depends on the content. Speech has a narrow frequency range and survives 48–64 kbps mono. Music with cymbals and reverb starts to sound smeared below about 128 kbps in MP3, or 96 kbps in Opus. See what bitrate means, interactively.

Format-specific guides and presets: MP3 compressor · WAV compressor · M4A and voice memo compressor.

Audio file size calculator

≈ 4.8 MB (192 kbps × 210 s ÷ 8)

Questions people ask

How do I compress audio to a percentage of its size?

Choose “By percentage” and drag to the size you want, for example 50% of the original. AudioKit converts that into the bitrate that lands on that size for your file’s length.

How do I reduce the size of an MP3 file?

Lower its bitrate. File size is simply bitrate × length, so re-encoding a 320 kbps MP3 at 128 kbps makes it 60% smaller. For speech, switching to mono and 64 kbps cuts it by 80% with little audible change.

How do I compress audio to fit an email or Discord?

Choose “To a target size”, enter the limit (8 MB for Discord free, 16 MB for WhatsApp audio, 25 MB for Gmail) and AudioKit calculates the highest bitrate that fits.

Does compressing audio lower quality?

Yes, lossy compression removes detail, and each pass removes a bit more. At 128 kbps and above most people can’t tell on music; at 64 kbps music gets swishy but speech is still clear. Opus handles low bitrates far better than MP3.

Why is my compressed file bigger than the original?

The original was already at a lower bitrate than the one you picked. Re-encoding at a higher bitrate only adds size. Check the “average kbps” shown for your file and pick something below it.

Is “compress audio” the same as a compressor effect?

No. Here it means making the file smaller. A dynamic range compressor, the studio effect, makes loud and quiet parts closer in volume; the volume booster’s normalise option does something similar for whole files.

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