The calculation, without hidden assumptions
A target-size bitrate calculation is bookkeeping, not a promise of visual quality. The file-size budget is converted to bits, divided by duration and then reduced by the audio bitrate and any safety margin you choose. Codec, content complexity and encoder settings still determine how good that bitrate looks.
How to use this calculator
Enter target file size and choose MB or MiB so decimal and binary units are not silently mixed.
Enter video duration and the audio bitrate you intend to keep.
Use the calculated average video bitrate as an encoder target, leaving the margin editable for container overhead or uncertainty.
Where people use it
- •Compressing video to upload limits
- •Planning email or platform file sizes
- •Comparing audio/video bitrate budgets
Example: 100 MB for 10 minutes
100 MB is 800,000,000 bits. Over 600 seconds that is about 1,333 kbps total before margin. Reserving 128 kbps for audio leaves roughly 1,205 kbps for video.
What the result does not assume
- •Actual encoded size can differ because of container overhead, variable bitrate behavior, metadata and encoder implementation. Use a margin and verify the exported file.
- •Bitrate alone does not determine quality; codec efficiency, resolution, frame rate, motion and source noise all matter.
Frequently asked questions
Why subtract audio bitrate?+
Audio and video share the same file-size budget, so the audio stream must be reserved before assigning the remaining average bitrate to video.
What is the difference between MB and MiB?+
MB uses 1,000,000 bytes; MiB uses 1,048,576 bytes.
Will the final file be exactly the target size?+
Not always. The result is an average budget; real encoders and containers add variability, which is why the margin is editable.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
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Keep the result connected to the real job
MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.