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Speed discrepancy: Mb/s and MB/s, or Mbps and MBps difference

If you see a big difference between the Internet connection speed your provider promised you, the speed you measured with other tools or speed tests, and the speed that NetWorx or NetGenius shows, it might mean that you are comparing bits (b) and bytes (B):

  • megabit (Mb) or megabit per second (Mbps, Mb/s), with a small or lowercase ‘b’; and
  • megabyte (MB) or megabyte per second (MBps, MB/s), with a capital or uppercase ‘B’.

Two units: bit and byte

One byte contains eight bits! Therefore anything measured in bits, kilobits, megabits or gigabits appears as a number that is about 8 times larger than the same thing measured in bytes, kilobytes, megabytes or gigabytes.

Many Internet service providers prefer using the higher, best-looking number in their marketing. For example, if one ISP offered 10 MB/s, while another ISP advertised their speed as 80 Mb/s, which one would most people choose? It may look like the second provider offers a much faster service, but in fact their speeds are equal. Customers should always pay attention to ‘b’ vs ‘B’.

In NetWorx, you can choose between bits and bytes by selecting your preferred Transfer rate unit in the Graph Settings. In NetGenius, you can make this choice in its Preferences.

Two systems: decimal and binary

Adding to the confusion is the fact that the industry uses two systems for measuring digital information: decimal and binary. In the decimal system the prefix kilo means 1000, while in the binary system kilo is 1024. Normally, the uppercase ‘K’ is used for the binary kilo units, while the lowercase ‘k’ is the correct prefix for the decimal kilo. The uppercase ‘M’ for mega, ‘G’ for giga and ‘T’ for tera are identical in both systems.

To distinguish the binary system more clearly, binary prefixes can be used: KiB (kibibyte) instead of KB (kilobyte), MiB (mebibyte) instead of MB (megabyte), and so on. But these prefixes don't seem to be popular in everyday use, and people still tend to say “kilobyte” referring to either 1000 or 1024 bytes. Either way, this difference is insignificant compared to the difference between bytes and bits.

Most commonly:

  • 1 kilobit (kb) = 1000 bits
  • 1 kilobyte (KB) = 1024 bytes = 1024 × 8 bits
  • 1 megabit (Mb) = 1000 kilobits = 1000 × 1000 bits
  • 1 megabyte (MB) = 1024 kilobytes = 1024 × 1024 × 8 bits

This means that to download 1 MB in 1 second you would need a connection speed of 1 MBps or 8 Mbps, because, depending on the system used, a megabyte (MB) is exactly or approximately 8 times the size of a megabit (Mb). The difference between a kilobyte (KB) and a kilobit (kb) is the same: a kilobyte is about 8 times larger than a kilobit. And a gigabyte (GB) is 8 about times larger than a gigabit (Gb).

Article details

Article ID: 10

Category: General product questions

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