Key takeaways
- The bitrate to set for a target size is target bytes × 8 ÷ seconds ÷ 1,000 minus the audio bitrate. When we used it for two-pass encodes, the files landed -1.75% to 0.36% from the target.
- A CRF encode ignored the target and came out about 10% under it, which is why a size limit needs two-pass or a bitrate mode.
- For 100 MB over a minute the budget is 13,981 kbps in total, 13,853 kbps for the picture.
How to use the bitrate
Set the video bitrate to the figure shown and keep the audio bitrate you entered. If the result is below about 1 Mbps for 1080p, the picture will suffer: lower the resolution or the length instead of pushing the bitrate down.
The calculator counts megabytes as 1,048,576 bytes. If the destination counts a megabyte as one million bytes, aim a few percent lower than the limit.
Scenarios
| Scenario | Total bitrate budget | Video bitrate to set | Audio takes |
|---|---|---|---|
| 25 MB, 1 minute | 3,495 kbps | 3,367 kbps | 938 KB |
| 25 MB, 3 minutes | 1,165 kbps | 1,037 kbps | 2.7 MB |
| 100 MB, 10 minutes | 1,398 kbps | 1,270 kbps | 9.2 MB |
| 100 MB, 1 minute | 13,981 kbps | 13,853 kbps | 938 KB |
| 500 MB, 1 hour | 1,165 kbps | 1,069 kbps | 41.2 MB |
| 10 MB, 30 seconds | 2,796 kbps | 2,732 kbps | 234 KB |
Measured: did the file hit the target?
| Output size | Target | Video bitrate set | Two-pass result | Error | CRF 28 result |
|---|---|---|---|---|---|
| 720p | 1.00 MB | 672 kbps | 1.00 MB | +0.36% | 897 KB (-10.3%) |
| 720p | 2.00 MB | 1472 kbps | 1.99 MB | -0.62% | 1.81 MB (-9.4%) |
| 720p | 5.00 MB | 3872 kbps | 4.93 MB | -1.48% | 4.60 MB (-7.9%) |
| 1080p | 1.00 MB | 672 kbps | 1.00 MB | +0.31% | 887 KB (-11.3%) |
| 1080p | 2.00 MB | 1472 kbps | 1.98 MB | -0.83% | 1.79 MB (-10.3%) |
| 1080p | 5.00 MB | 3872 kbps | 4.91 MB | -1.75% | 4.55 MB (-9.0%) |
These runs use the same 10 second 1080p excerpt as the video compressor page.