Practical audio guide
Audio File Size and Bitrate Calculator
Use the calculator for planning, then verify the encoded output. It reserves a configurable overhead margin because containers and metadata consume some of the target budget.
Key takeaways
- Calculate size when duration and bitrate are known.
- Calculate bitrate when duration and a hard size limit are known.
- Leave 2–5% overhead margin for uploads with strict byte limits.
- Treat the result as an estimate until the real file is encoded.
Interactive calculator
Plan the encode before uploading
Formula used for estimated file size
Size in bytes is approximately bitrate in bits per second multiplied by duration in seconds, divided by eight. The calculator reports decimal MB and binary MiB so a platform's convention is easier to recognize.
Formula used for a target size
Available bitrate is target bytes multiplied by eight, reduced by the selected overhead margin, then divided by duration. The tool reports total audio bitrate; do not multiply it again by the channel count.
Choose a realistic result
If calculated MP3 bitrate is below roughly 64 kbps for music, quality is likely to be heavily compromised. Speech may remain useful at lower values, especially in mono, but splitting or shortening the recording is often better.
Method and sources
Examples use controlled synthetic references so settings are reproducible and no private user audio is involved. Production runs FFmpeg 5.1.9; benchmark fixtures were generated and verified with FFmpeg 8.1.2.