Reviewed answer
How do I calculate video file size from bitrate?
Multiply the combined video and audio bitrate by the duration in seconds, then divide by eight to convert bits to bytes. Divide again by 1,000,000 for an approximate decimal megabyte value.
Claims reviewed 2026-10-16.
The estimate is: file size in bytes = total bitrate in bits per second × duration in seconds ÷ 8.
Variable-bitrate encoding and container overhead make the final file slightly different, so use the result for planning rather than as an exact output guarantee.
Example
A five-minute video at 8 Mb/s video plus 0.192 Mb/s audio is approximately 307 MB before allowing for container overhead.