MP3 bitrate explained: 128, 192 or 320 kbps?
What bitrate means, how it changes file size, and which setting makes sense for speech and for music.
What bitrate means
Bitrate is how much data is used for each second of audio, measured in kilobits per second (kbps). More data means the encoder has to throw away less, so higher bitrates sound closer to the original — up to the point where you stop hearing a difference.
How it changes file size
File size follows directly from bitrate: divide by eight to get bytes per second. A minute of MP3 at 128 kbps is about 0.96 MB, at 192 kbps about 1.44 MB, and at 320 kbps about 2.4 MB. Tonify shows the estimated size for your chosen bitrate before the conversion starts.
Which bitrate for what
Speech — lectures, interviews, voice notes — sounds fine at 128 kbps. For music, 192 kbps is a sensible middle ground. 320 kbps is the highest bitrate the MP3 format allows; pick it when the source is good and space is not a concern.
The source sets the ceiling
A higher bitrate cannot restore detail that the video's own audio track never had. If the video was recorded on a phone or saved from a messaging app, its audio is already compressed; choosing 320 kbps gives you a bigger file, not a noticeably better one. When in doubt, try 192 kbps and listen.
Try it on your iPhone
Tonify pulls the audio out of any video as MP3, M4A or WAV, or cuts a 30-second ringtone — converted on your phone, with no upload.
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