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Bitrate measures how much data per time is used in a recording.

A megabit is a unit of digital information storage, abbreviated Mbit (or Mb).

1 megabit = 1,000,000 bits which is equal to 125,000 bytes. In kilobytes this is either 125 kB (decimal units, where 1 kilobyte = 1000 bytes) or about 122 kiB (binary units, where 1 kibibyte = 1024 bytes). The megabit is most commonly used when referring to data transfer rates in network speeds, e.g. a 100 Mbit/s (megabit per second) Fast Ethernet connection. In this context, like elsewhere in telecommunications, it always equals a million bits. Residential high speed Internet access is often advertised incorrectly in megabits (a unit of information) rather than megabit per second.

Video streams are often referred to as being "N megabit" streams (which means N Mbit / second). Novice users often confuse Megabits and Megabytes. There are 8 bits in 1 byte; likewise there are 8 Megabits in 1 Megabyte (so divide Mb/sec by 8 to get MB/sec).

Here are some helpful numbers:

Megabit values
Source Mb/sec MB/sec MB/hour GB/hour MiB/sec MiB/hr GiB/hr
N/A 1.0 0.125 450 0.45 0.119 429 0.419
DVD (max peak bitrate) 10.08 1.260 4536 4.536 1.202 4326 4.224
HD-PVR Recording (adjustable settings) 13.5 1.6875 6075 6.075 1.6093 5793 5.658
HD Recording (ATSC) (max bitrate) 19.4 2.425 8730 8.73 2.313 8326 8.130

Conversions between Mb/sec to MB/sec - Google is your friend

One of the easiest ways to perform megabit to megabyte conversion (aside from dividing by 8) - is to go to enter a query on google with the terms "X Mb/sec to MB/sec" (replace X with the megabit value you wish to convert)

Note that Google does not distinguish between binary and SI prefixes, so when using this approach, the "byte" units will be treated as binary (i.e. GB or gigabyte will be treated as gibibyte).