
Gigabit
The gigabit is a multiple of the unit bit for digital information or computer storage. The prefix giga (symbol G) is defined in the International System of Units (SI) as a multiplier of 109 (1 billion, short scale), and therefore
1 gigabit = 109bits = 1000000000bits.The gigabit has the unit symbol Gbit or Gb.
Using the common byte size of 8 bits, 1 Gbit is equal to 125 megabytes (MB) or approximately 119 mebibytes (MiB).
The gigabit is closely related to the gibibit, a unit multiple derived from the binary prefix gibi (symbol Gi) of the same order of magnitude, which is equal to 230bits = 1073741824bits, or approximately 7% larger than the gigabit.

Megabit
The megabit is a multiple of the unit bit for digital information. The prefix mega (symbol M) is defined in the International System of Units (SI) as a multiplier of 106 (1 million), and therefore
1 megabit = 106bits = 1000000bits = 1000 kilobits.The megabit has the unit symbol Mb or Mbit.
The megabit is closely related to the mebibit, a unit multiple derived from the binary prefix mebi (symbol Mi) of the same order of magnitude, which is equal to 220bits = 1048576bits, or approximately 5% larger than the megabit. Despite the definitions of these new prefixes for binarybased quantities of storage by international standards organizations, memory semiconductor chips are still marketed using the metric prefix names to designate binary multiples.
Using the common byte size of eight bits and the standardized metric definition of megabit and kilobyte, 1 megabit is equal to 125 kilobytes (kB) or approximately 122 kibibytes (KiB).
The megabit is widely used when referring to data transfer rates of computer networks or telecommunications systems. Network transfer rates and download speeds often use the megabit as the amount transferred per time unit, e.g., a 100 Mbit/s (megabit per second) FastEthernet connection, or a 10 Mbit/s Internet access service, whereas the sizes of data units (files) transferred over these networks are often measured in megabytes. To achieve a transfer rate of one megabyte per second one needs a network connection with a transfer rate of eight megabits per second.

Gigabit (noun)
10^{9} bits, a thousand million (1,000,000,000) bits.

Gigabit (noun)
2^{30} (1,073,741,824) bits.

Megabit (noun)
10^{6} = 1,000,000 bits or 125,000 bytes (125 kilobytes).

Megabit (noun)
2^{20} = 1,048,576 bits; a mebibit.

Gigabit (noun)
a unit of information equal to one thousand million (10⁹) or (strictly) 2³⁰ bits.

Megabit (noun)
a unit of data size or (when expressed per second) network speed, equal to one million or (strictly) 1,048,576 bits.