In order to explain this let's go down to the difference of a bit to a byte.

A bit (short for ‘binary digit’) is the smallest unit of digital

information; simply a 1 or a 0. A byte is a group of eight bits.

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Scaling these up, 1 Megabit (MBit / Mb) is 1000,000 bits, and 1 MegaByte

(MByte / MB) is 1000,000 bytes, and, as there are 8 bits

in every byte, there are 8 Megabits in every MegaByte.

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So, in short, 1 Megabit is 1 million ‘1’s and ‘0’s, while 1 MegaByte

is 8 million ‘1’s and ‘0’s.

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Confusingly both terms are commonly used in computing; MegaBits

are most often used for measuring an Internet connection

download or upload speeds, while Megabytes are used to measure file size.

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In terms of download and upload speeds, when someone says a connection

is “30 Megabits per second” this needs to be divided by eight to find

the “MegaBytes per second” that will be transferred.

The most common way people are confused is when speeds

(eg 30 Megabits/Megabytes per second) are written in short forms like

30Mbps or 30MBps without additional clarification as to whether

the ‘b’ is representing a bit or a byte, compared to the much

clearer ‘30MBit/s’ or ‘30MByte/s’. The common convention for the

shortened form, is that a lowercase ‘b’ represents bits, while a

uppercase ‘B’ represents bytes.