Settings for this task
| Use case | Setting | What to check |
|---|---|---|
| Strict upload budget | Next smaller target preset | Leave space for unit differences and encoding overhead. |
| Long spoken session | Shorter excerpt first | Removing irrelevant minutes can preserve a useful bitrate. |
How to use this tool
- Upload the audio so the server can measure its duration.
- Select one of the displayed targets from 1 to 25 MiB.
- Process and compare the final size against the actual receiving limit.
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 | 64 kb/s | 4.8 MB |
| 10:00 | MP3 | 128 kb/s | 9.6 MB |
| 1:00:00 | MP3 | 64 kb/s | 28.8 MB |
The calculation used by this tool
The implementation multiplies the target by 1,048,576 bytes, reserves 2%, converts to bits and divides by duration and 1,000. It floors the result and clamps it to 32–320 kbps. The target presets are labelled binary MiB; a strict decimal-MB service counts 1,000,000 bytes instead.
When a target is impossible
Estimated payload at 32 kbps: one hour needs about 14.4 decimal MB. Asking for 5 MB cannot overcome that lower bound. Conversely, a short clip may remain well below a large target because the processor stops increasing bitrate at 320 kbps. It does not pad files to fill the budget.
Verify the encoder's actual result
MP3 encoders use supported bitrate steps, and headers or metadata occupy additional bytes. This implementation does not run an iterative size-fitting loop after encoding. If the output is slightly too large, choose a smaller preset; if it is much too large, reconsider the duration or delivery method.
Questions about this operation
- Is this an exact byte-size converter?
- No, it calculates a bitrate toward the target. The final download is the authoritative size.
- Does choosing 10 MiB mean 10,000,000 bytes?
- Not here: the processor uses 10 MiB before reserving overhead. Choose a lower preset for a strict decimal limit.
- Can I force 320 kbps under any target?
- No. Duration times bitrate determines the payload size; both requirements may be incompatible.
- Why does the bitrate control not change my target result?
- In target mode the processor calculates bitrate from size and duration. Use a bitrate-based compressor when you want to choose that value directly.
- Will voices remain clear at the minimum?
- That depends on the recording. Test names and quiet speakers; a successful size calculation is not a listening-quality guarantee.