Every converter asks this and almost none of them explain it. Bitrate is how many bits of data each second of audio is allowed to use. More bits means more of the original detail is kept and a larger file; fewer bits means a smaller file and more thrown away. That is the entire trade.
The arithmetic is simple enough to do in your head: divide the bitrate by 8 to get kilobytes per second. A 192 kbps MP3 uses 24 kB every second, which is 1.44 MB a minute.
| Bitrate | Per minute | A three-minute track | An hour |
|---|---|---|---|
| 320 kbps | 2.4 MB | 7.2 MB | 144 MB |
| 256 kbps | 1.9 MB | 5.8 MB | 115 MB |
| 192 kbps | 1.4 MB | 4.3 MB | 86 MB |
| 128 kbps | 0.96 MB | 2.9 MB | 58 MB |
The short answer
- Music you will listen to: 192 kbps. This is where most listeners on most equipment stop being able to tell. It is the default here for that reason.
- Music from a lossless master: 256 or 320 kbps. If the source is FLAC, WAV or AIFF, this is the first lossy step the audio has ever taken and the only copy your listeners get. Do not economise on it.
- Speech — interviews, lectures, voice memos: 128 kbps, and mono if the recording is mono. A voice occupies far less of the spectrum than music does.
- A phone call or an AMR recording: 64 kbps mono. The source is 8 kHz telephone audio. A higher setting stores its limits in greater detail; it does not lift them.
What VBR actually does
Constant bitrate gives every second the same allowance, whether it is a dense orchestral passage or four seconds of silence. Variable bitrate lets the encoder spend where the music is complicated and save where it is not, aiming at a quality target rather than a size target.
The practical result is a smaller file at the same perceived quality, or better quality at the same size — with two costs. The final size is not predictable before you encode, which matters if you are filling a device or meeting an upload limit. And a small number of very old hardware players handle VBR badly, usually by reporting the wrong track length or seeking inaccurately.
If you know what device the file is going to, VBR is the better choice. If you need a predictable size, or the file is going somewhere unknown, use constant bitrate.
The thing bitrate cannot do
Bitrate is a ceiling, not a floor. Converting a 96 kbps file to 320 kbps produces a 320 kbps file that sounds exactly like the 96 kbps one, in a container three times the size. The encoder can only work with what reaches it, and what reaches it is whatever the previous encoder left behind.
This is why the source format matters more than the setting:
- From FLAC, WAV or AIFF — nothing has been discarded yet. A high bitrate is genuinely worth paying for.
- From AAC, M4A, OGG or Opus — one lossy pass has already happened, and this is the second. Use 192 kbps or above so the second pass stays inaudible, and convert from the best copy you have rather than from a copy of a copy.
- From AMR — the recording was band-limited to 8 kHz when it was made. 64 kbps already carries all of it.
Does 320 kbps sound better than 192?
Measurably, yes: it discards less. Audibly, for most people on most equipment with most music, the honest answer is that it is very hard to tell, and listening tests have said so for a long time. The difference is easiest to hear on dense material — massed strings, cymbals, applause — on good headphones, listening attentively for it.
Which does not make 320 pointless. It costs disk space and nothing else, and it means the copy you are making survives being played on better equipment than you own now. If you are keeping the lossless source anyway, 192 is fine; if the MP3 is your copy, take 320.
Where the setting lives
The bitrate and VBR controls sit behind the Adjust key on every conversion page — one layer down, because the default path is meant to be drop a file and press the red key. The setting you choose applies to the conversion you run next, including a batch of several files.
If you are converting from WAV, the companion piece to this one is how to convert WAV to MP3, which works through the whole procedure and what the compression costs.