The calculation
A worked example
A 20-minute video at a combined video + audio bitrate of 25 Mbps is approximately 3.75 GB, before container overhead.
Bitrate is the missing ingredient
Resolution alone does not determine file size. Two 4K videos can have very different sizes because of codec, frame rate, content complexity and quality settings. Use the average bitrate of your intended export, including audio, rather than the camera’s recording setting if you are re-encoding.
Average versus maximum
For variable bitrate encoding, a maximum bitrate is a ceiling, not the average over the whole video. A target average is a better planning input, but a completed export is still the best evidence. Add margin for container metadata, extra audio tracks and uncertainty. This calculator does not predict visual quality or recommend one bitrate for every platform.
Source & further reading
YouTube: recommended upload encoding settings
Model reviewed October 25, 2026. Read our methodology and limitations.