How much smaller will my audio file get?

File size is bitrate multiplied by duration. Going from 320 kbps to 128 kbps makes the file roughly 2.5 times smaller. The page estimates the result before you convert.

Does compressing audio lose quality?

Yes. MP3 is lossy, so lowering the bitrate discards more detail permanently. For speech the loss is hard to notice even at 64 kbps; for music, staying at 128 kbps or above is safer.

Can I compress without losing any quality?

Not with MP3. If the source is WAV or FLAC, converting to a lossless format like FLAC shrinks it with no quality change at all — use the audio format converter for that.

What bitrate should I choose for a podcast?

64 to 96 kbps mono is standard for spoken word and keeps an hour-long episode under about 40MB. Music needs more: 128 kbps as a floor, 192 or higher for careful listening.

Compress Audio

Make an audio file smaller so it fits an email or upload limit. Pick a quality level and see the estimated size before converting. Free, no sign-up. Files auto-deleted after 15 minutes.

Drop your audio file here

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MP3, WAV, FLAC, M4A, OGG, OPUS, AIFF • Max 100MB

Compression level

Channels

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How audio compression works

The size of an MP3 is almost entirely decided by one number: the bitrate, measured in kilobits per second. A file's size is roughly its bitrate multiplied by its duration, so halving the bitrate halves the size. Nothing else you can change comes close to having that much effect.

That is why this page asks for a quality level rather than a target size directly. Once you pick a level, the size follows from how long your audio is, and the estimate above updates as soon as your file loads.

Which level should you pick?

64 kbps — Speech only. Voice memos, interviews, lecture recordings. Music at this bitrate sounds noticeably poor.
96 kbps — Podcasts and audiobooks. An hour fits in about 40MB.
128 kbps — The safe default. Acceptable for music, small enough for most limits.
192 kbps — Music you actually listen to. A reasonable balance.
256 kbps — Only a modest saving over a 320 kbps source, but keeps almost all the detail.

Switching to mono roughly halves the size again. It is the right call for anything spoken, and the wrong call for music with any stereo image worth keeping.

Compression is permanent

MP3 is a lossy format: lowering the bitrate throws audio data away, and converting back up later does not bring it back. Compress a copy, not your only version, and start from the highest-quality source you have rather than from something already compressed.

If your source is WAV or FLAC and you want a smaller file with no quality loss at all, convert to FLAC instead with the audio format converter — lossless compression typically saves 40 to 50 percent.

Frequently asked questions

How is this different from Change Audio Quality?

Same engine, different question. Change Audio Quality exposes bitrate, sample rate and channels for when you know exactly what you want. This page asks only how small you need the file and shows you the result up front.

Is the estimated size exact?

Close, but not exact. The estimate assumes a constant bitrate and ignores tags and cover art, so the real file usually lands within a few percent.

Will my tags survive?

Title, artist and album normally carry over. Check the result in the tag editor if the file matters.

Related guides

MP3 bitrate guide — what each bitrate actually sounds like
How to change MP3 audio quality — bitrate, sample rate and channels explained
Convert audio format online — lossless options such as FLAC