What Each Bitrate Sounds Like
Rough guide for stereo audio:
- 320 kbps - transparent for nearly all listeners; ~2.4 MB/min.
- 256 kbps - effectively indistinguishable from 320 for most material; ~1.9 MB/min.
- 192 kbps - very good; slight softening of cymbals and dense mixes; ~1.4 MB/min.
- 128 kbps - acceptable for casual listening; artifacts audible on good gear; ~1 MB/min.
- 64 kbps - noticeably degraded for music, but fine for mono speech; ~0.5 MB/min.
Voice content tolerates low bitrates far better than music - see our podcast bitrate guide.
Step by Step: Compressing on mp3.now
- Open the MP3 compressor (or the bitrate changer for direct control).
- Upload your MP3 - drag and drop or click to browse.
- Choose the target bitrate from the options panel. Shortcuts exist for common targets: 128 kbps, 64 kbps, or 192 kbps.
- Click Convert and wait a few seconds.
- Download the compressed file and check the new size.
Two More Levers: Channels and Sample Rate
Bitrate is not the only knob. Converting stereo to mono halves the data the encoder must describe - ideal for speech, where stereo adds nothing. Reducing the sample rate from 44.1 kHz to 22.05 kHz can also shrink voice recordings, at the cost of high-frequency content. For music, leave both alone and adjust bitrate only.
Mistakes to Avoid
Never compress upward: converting a 128 kbps file to 320 kbps makes it larger without restoring any quality, because the discarded detail is gone. Avoid repeated re-compression of the same file - each pass stacks artifacts. And keep an original copy before compressing; on mp3.now your source file is only retained temporarily (24 hours for guests, 7 days with a free account), so the archival copy should live with you.
How Much Smaller Will Your File Get?
The savings are exactly proportional to the bitrate change, so you can predict the result before converting. A 10-minute stereo recording works out roughly like this:
| Bitrate | Size (10 min) | vs 320 kbps |
|---|---|---|
| 320 kbps | ~24 MB | - |
| 192 kbps | ~14.4 MB | 40% smaller |
| 128 kbps | ~9.6 MB | 60% smaller |
| 64 kbps (mono speech) | ~4.8 MB | 80% smaller |
This math also tells you which account tier you need: a large source file must fit the upload limit before compression, so a 30 MB MP3 needs at least a free account's 50 MB allowance even though the output will be small.