MP3 Bitrate Explained: CBR vs VBR and What Quality to Choose
When you save an MP3, the main setting is the bitrate: how many kilobits of data are used for each second of audio. It controls both the file size and the quality.
Bitrate and file size
Size is simple to estimate: bitrate × duration ÷ 8. At 128 kbps, one minute is about 0.96 MB. At 64 kbps it is about 0.48 MB, and at 320 kbps it is about 2.4 MB. Doubling the bitrate doubles the size.
CBR, VBR and ABR
- CBR (constant bitrate): every second of audio gets the same amount of data, whether it is silence or a complex sound. File size is exactly predictable. It is also the most compatible mode, because every player and platform handles it.
- VBR (variable bitrate): the encoder spends more bits on complex passages and fewer on simple ones, aiming for a quality level rather than a fixed rate. It usually gives better quality for the same size, but the size is less predictable.
- ABR (average bitrate): a compromise: the rate varies but the average stays near a target.
The Sayvoi converter encodes MP3 at a constant bitrate that you choose, from 64 to 320 kbps. That keeps file sizes predictable, which matters when you must stay under an upload limit.
Which bitrate for what
| Content | Suggested bitrate |
|---|---|
| Speech for listening on phones, voice notes | 64 to 96 kbps |
| Podcasts and general speech | 96 to 128 kbps |
| Music, good quality | 192 to 256 kbps |
| Music, highest MP3 quality | 320 kbps |
Sample rate and channels matter too
- MP3 supports sample rates of 8, 11.025, 12, 16, 22.05, 24, 32, 44.1 and 48 kHz. Lower sample rates allow lower maximum bitrates, so a 16 kHz file will not use 320 kbps.
- For a single voice, convert to mono. The encoder then spends all of its bits on one channel, so 64 kbps mono often sounds better than 64 kbps stereo.
MP3 is not for masters or datasets
MP3 is lossy, and every encode removes detail you cannot get back. Keep your original WAV or FLAC for archives and for project delivery that requires lossless audio. Read WAV vs MP3 vs FLAC to decide, and how to convert WAV to MP3 for the steps.
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