How this calculator works
First divide the target size by one plus the overhead rate. Convert the usable bytes to bits per second over the full duration, then subtract the audio bitrate.
The formula
(target bytes ÷ (1 + overhead) × 8 ÷ duration seconds) − audio bitrateBitrates are normalized to bits per second, durations to seconds, and storage to bytes before calculation.
Worked examples
- A 1 GB target for 1 hour with 128 Kbps audio and no overhead leaves about 2.09 Mbps for video.
- A 500 MB target for 20 minutes with 128 Kbps audio and 1% overhead leaves about 3.17 Mbps for video.
- A 4 GiB target for 2 hours with 256 Kbps audio and 1% overhead leaves about 4.47 Mbps for video.
Frequently asked questions
Does a higher bitrate always look better?
Higher bitrate can preserve more detail, but quality also depends on codec, encoder settings, motion, and source footage.
Why does the calculator reject a small target?
The requested size cannot hold the audio stream for the full duration, so no positive video bitrate remains.