MP3 bitrate explained: 128 vs 192 vs 320 kbps

When you convert a video to MP3, the first choice you face is the bitrate: 128, 192, 256 or 320 kbps. It decides both the sound quality and the file size. Here is what those numbers really mean and how to pick the right one in a few seconds.

What is bitrate?

Bitrate is the number of kilobits used to describe one second of sound. A CD stores uncompressed audio at 1,411 kbps. MP3 reaches 128–320 kbps by throwing away information the human ear is unlikely to notice – very high frequencies, quiet sounds hidden by louder ones (what engineers call psychoacoustic masking). The fewer kilobits you allow, the more the encoder has to discard.

File size per bitrate

The calculation is simple: bitrate × duration ÷ 8. For one minute of audio:

Can you hear the difference?

Below 128 kbps, most people notice artefacts in music: a “swirly” sound on cymbals, a narrower stereo image, less sparkle. Between 128 and 192 kbps, the difference is subtle and depends on the music and the headphones. Above 192 kbps, controlled blind tests (ABX tests) show that very few listeners can reliably distinguish 256 or 320 kbps from the original with modern encoders such as LAME. On phone speakers, Bluetooth earbuds and in the car, the difference disappears completely – Bluetooth itself re-compresses the audio.

The golden rule: you cannot add quality

A converter can only keep or lose quality, never create it. Most phone videos store their sound in AAC at 128 to 256 kbps; a video downloaded from a social network may contain 96–128 kbps. Exporting such audio at 320 kbps produces a bigger file that sounds exactly the same as a 192 kbps one. As a rule of thumb, choose a bitrate equal to or slightly higher than the source.

Which bitrate should you choose?

• Lectures, meetings, interviews, podcasts: 128 kbps (or Opus 64–96 kbps for the smallest files).
• Music for everyday listening: 192 kbps – the default in our converter.
• Music you want to keep in MP3 for the long term: 256 or 320 kbps.
• Audio you will edit, mix or master: do not use MP3 at all – choose WAV or FLAC.

CBR, VBR and ABR

MP3 can be encoded at a constant bitrate (CBR: every second uses the same number of bits), a variable bitrate (VBR: complex passages get more bits, silence gets fewer) or an average bitrate (ABR). VBR gives the best quality for a given file size, but CBR is the most compatible with old players and makes the duration display exact. Videos-to-MP3 uses CBR for maximum compatibility; with FFmpeg you can request VBR with -q:a 2 (around 170–210 kbps).

Sample rate is not bitrate

The sample rate (44.1 kHz or 48 kHz) describes how often the sound wave is measured; the bitrate describes how much data is kept after compression. Both matter, but for MP3 you only need to choose the bitrate: the encoder keeps the source sample rate (usually 48 kHz for video, 44.1 kHz for music).

And other formats?

At the same bitrate, AAC (M4A) and Opus sound better than MP3: AAC at 128 kbps is roughly equivalent to MP3 at 160–192 kbps, and Opus at 96 kbps rivals MP3 at 160 kbps. If your player supports them, they save space. The full comparison is in MP3 vs AAC vs WAV vs FLAC vs OGG vs Opus.