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Speed discrepancy: MB/s and Mb/s 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 shows, 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 unit used for file sizes and often in the end user software, and
  • megabit (Mb) or megabit per second (Mbps, Mb/s), with a small or lowercase ‘b’ — a unit used for download speeds advertised by ISPs and reported by on-line tools.

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 exactly the same.

In NetWorx, you can choose between bits and bytes by selecting your preferred Transfer rate unit in the Graph Settings.

Article details

Article ID: 10

Category: NetWorx: technical questions and how-to

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