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GivenTool

Compress an audio file

Shrink audio files with a bitrate, mono and sample-rate choice, and see the expected size first.

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Drop a file here or click to browseAccepts MP3, M4A, AAC, OPUS, OGG, OGA, WAV, WEBM, FLAC, WMA, AMR. Up to 200.0 MB per file.

The size of a compressed audio file is almost entirely decided by one number: the bitrate, in kilobits per second. A one-hour recording at 128 kbps is about 58 MB; at 64 kbps it is about 29 MB; at 32 kbps, 14 MB. This tool shows that estimate as soon as it knows the length of your file, before you encode anything, together with the size of the original, so you can pick the lowest bitrate that still sounds right for the content.

For speech (lectures, interviews, meetings, voice notes), mono at 32-64 kbps is clear and tiny, because a single voice does not need two channels. Music needs more: 128 kbps stereo is the usual floor for MP3, 160-192 kbps for critical listening. Opus, the codec behind WhatsApp voice messages, sounds noticeably better than MP3 at low bitrates and is the smallest option, but some older players cannot open .opus files; MP3 plays everywhere and M4A (AAC) suits Apple devices. The automatic sample-rate setting lowers the sample rate for very low bitrates, which avoids the swirly artefacts MP3 makes when it has too few bits for 44.1 kHz.

Compression is lossy and one-way: it cannot make a low-quality file sound better, and a file that is already 64 kbps will not improve at 128. If the estimate is larger than the original, the page says so. The encoding runs in your browser with FFmpeg in WebAssembly (a one-time 32 MB download), and metadata such as tags and cover art is removed. Files up to 200 MB are accepted.

How to use it

  1. Drop an audio file: MP3, M4A, AAC, WAV, FLAC, OGG, Opus, WebM, WMA or AMR.
  2. Pick a preset (voice note, podcast, music, smallest) or set the format, bitrate, channels and sample rate yourself.
  3. Check the estimated size against the original.
  4. Click Compress audio, listen to the result and download it.

Frequently asked questions

What bitrate should I use?

Speech: 32-64 kbps mono. Podcasts: 64-96 kbps mono. Music: 128 kbps stereo, or 160-192 kbps if quality matters. Below 32 kbps, choose Opus rather than MP3.

How accurate is the size estimate?

MP3 at a constant bitrate usually lands within a few percent. AAC and Opus adapt to the content, so the real size can differ more; the result shows the actual size.

Does converting to mono lose anything?

The left and right channels are mixed into one. For a single voice nothing audible is lost; for music the stereo width disappears.

Why is there no estimate for my file?

The estimate needs the duration, which the browser reads while loading the file. For formats it cannot play (some WMA or AMR files) the duration is unknown until FFmpeg processes it; compression still works.

Can I compress to an exact size, such as under 10 MB?

Pick the bitrate whose estimate is just under your limit. As a rule, bitrate in kbps = size in MB × 8,000 ÷ duration in seconds.

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