Settings for this task
| Use case | Setting | What to check |
|---|---|---|
| Music copy | 192 kbps · stereo | Compare cymbals and room ambience. |
| Podcast | 96 kbps · mono | Suitable starting point for a single voice. |
| Small voice attachment | 64 kbps · mono | Check names, numbers and consonants carefully. |
How to use this tool
- Upload the MP3 and inspect its original bitrate.
- Choose a lower bitrate in Advanced settings; retain stereo for spatial music.
- Compare a quiet passage and a busy passage in the downloaded copy.
Calculated size examples
Calculated, not measured uploads: bytes ≈ bitrate (kb/s) × seconds × 1,000 ÷ 8. MB here means 1,000,000 bytes. Headers, tags and variable bitrate affect actual size. Channels are already included in the total bitrate; do not multiply again.
| Output duration | Format | Bitrate | Estimated audio payload |
|---|---|---|---|
| 10:00 | MP3 | 320 kb/s | 24 MB |
| 10:00 | MP3 | 192 kb/s | 14.4 MB |
| 10:00 | MP3 | 128 kb/s | 9.6 MB |
| 10:00 | MP3 | 96 kb/s | 7.2 MB |
| 10:00 | MP3 | 64 kb/s | 4.8 MB |
MP3-to-MP3 generation loss
The encoder does not simply remove unused bytes. It decodes the source and compresses the sound again, potentially accentuating watery speech, smeared percussion or metallic high frequencies. Converting 96 kbps to 320 kbps before compressing does not help; it only creates another generation.
Reading the size ladder
The table holds duration at ten minutes, so bitrate is the only changing variable. The ratio 128/320 predicts about 40% of the audio payload, not an exact whole-file reduction. Artwork and tags matter more in very short clips. At a fixed total bitrate, switching stereo to mono does not itself halve the bytes.
Constant and variable bitrate
The visible bitrate control supplies an encoding bitrate. The backend also understands VBR, but this interface does not expose a CBR/VBR selector. Do not interpret a displayed bitrate as a promise that every second or every MP3 frame has precisely that size.
Questions about this operation
- Can MP3 compression be lossless?
- Lower-bitrate re-encoding is lossy. If you only need a shorter file, cutting unwanted material may avoid re-encoding when stream copy is possible.
- Why is my 64 kbps MP3 not smaller?
- The default 160 kbps setting is higher than your source. Keep that source or shorten it instead of assuming every preset shrinks it.
- Should I choose 256 or 192 kbps?
- Try 192 for sharing and compare it with the original. Use 256 if difficult musical passages sound worse and the size budget allows it.
- Will mono preserve an interview?
- Usually it retains speech, but two channels can contain separate speakers. Listen to the mixed result before discarding either channel's separation.
- What if the uploaded file is rejected?
- This page accepts MP3 only. Use the general audio compressor for WAV, M4A or another supported source; renaming its extension is not conversion.