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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 NetMaster show, it might mean that you are comparing bytes and bits.

One thing that often causes confusion is the difference between:

  • megabyte (MB) or megabyte per second (MBps, MB/s), with a capital or uppercase ‘B’, a data-rate unit used for file sizes and often in end-user software, equal to 10002 bytes (B); and
  • megabit (Mb) or megabit per second (Mbps, Mb/s), with a small or lowercase ‘b’, a data-rate unit used for download speeds advertised by ISPs and reported by on-line tools, equal to 10002 bits (b).

People often incorrectly assume that a speed of 1 Mbps will allow them to download 1 MB in 1 second. This is not the case, because one byte contains eight bits, thus making a megabyte 8 times the size of a megabit; so to download 1 MB in 1 second you need a connection speed of 8 Mbps. The difference between a gigabyte (GB) and a gigabit (Gb) is the same: a gigabyte is 8 times larger than a gigabit.

An additional complication comes from the fact that file size is typically measured in binary system, which used to refer to kilobyte as 210 = 1024 bytes, megabyte as 10242 bytes, and gigabyte as 10243 bytes. These units are now used with IEC binary prefixes: KiB (pronounced “kibibyte”), MiB (mebibyte) and GiB (gibibyte).

In this confusing situation, 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 identical.

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

Article details

Article ID: 10

Category: General product questions

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