Bitrate vs Size Calculator

Bitrate is a rate of data over time, so file size is the accumulated bitrate across the whole duration. A small bitrate change can look harmless per second, but over long videos it compounds into hundreds of megabytes. Audio, container overhead, and streaming headroom are smaller terms, but they still shift the final delivery budget.

Bitrate is measured in bits per second, but file size is in bytes — and one byte is 8 bits. So the megabits per second your encoder shows must be divided by 8 to get megabytes per second of storage. A quick rule of thumb: 8 Mbps is roughly 1 MB every second, so a 10-minute clip lands near 600 MB before audio and overhead. Getting this factor of 8 right is the difference between a plan that fits and one that overflows eightfold.

Bitrate always uses the SI mega: 1 Mbps is exactly 10⁶ bits per second. But 'MB' for file size is ambiguous — storage vendors and this calculator treat it as 10⁶ bytes, while Windows still counts in base-2 units where one 'MB' is really 2²⁰ = 1,048,576 bytes (properly a mebibyte, MiB). So the same 700 MB file can read as 668 MB in your file browser, and the gap compounds with each prefix step until a '1 TB' drive shows only about 931 GB.