kb/s (kilo bits per second) notation with a small b
kB/s (kilo bytes per seconds) notation with a large B
8 bits = 1 byte = 1 octect
1000 octect = 1kb
1024ko = 1Mo
The formula to calculate the weight of a video according to its constant bitrate is the following:
bit rate in kb/s x duration in seconds / 8 / 1024 = size in MB
Example for a video of 1728 Kb/s (1600kb/s for the video stream and 128kb/s for the audio)
To calculate the weight of one minute of video we have 1728 (kb/s) * 60 (s) / 8 / 1024 which gives 12,65625mo for 1min.
To calculate the weight of one hour of video we have 1728 (kb/s) * 3600 (s) / 8 / 1024 which gives 759,375mo for 1h or 0,75Go / h.