Whats the difference between kbps and kBps ? A lot.

There is a big difference between 56 kbps or 56 kBps. If you are writing a technical paper and you are a programmer from SAP, make sure you get it right because the difference between bits and bytes is huge.

The correct convention is to use a small “b” for bits, and capital “B” for bytes and there are eight bits to a byte.

56 kbps = 56000 bits per second
56 kBps = 8 * 56000 = 448000 bits per second

Spread the word.

Mibi Mega Kibi Kilo – Decimal and Binary Prefixes

Wikipedia Data Rate Units

  • http://electronauts.wordpress.com/ electronauts

    56 kbps = 57344 bits per second
    1 kbps = 1024 bits per second

    • http://www.larsenconsulting.net Robert Larsen

      Nope — not in networking terms. In computing terms:
      1 kilobit = 1024 bits
      1 megabit = 1024 * 1024 bits
      1 gigabit = 1024 * 1024 * 1024 bits

      But in networking:
      1kbps = 1,000 bps
      1Mbps = 1,000,000 bps
      1Gbps = 1,000,000,000 bps

      It’s amazing how many people in the wider IT industry don’t realise that difference. :-)

      • http://etherealmind.com Greg Ferro

        You are quite wrong. Consult the standards referenced in the post.

        1 kibibit = 1024 bits.
        1 Mibibit = 1024 * 1024 bits.

        Time to update your knowledge. There are ‘decimal’ bits per second and ‘binary’ bits per second and there is nomenclature to denote it.

        • http://www.larsenconsulting.net Robert Larsen

          Not sure how I’m wrong here… does not Gigabit Ethernet run at 1,000,000,000 bits per second? Maybe it’s my terminology that’s wrong — you’re saying that my computing terms above should have used kibi-, mebi-, gibi-, etc.? I can’t ever remember anyone use those terms except when discussing them in this kind of context (i.e. people still use old-school kilo, mega and giga for binary computing terms in the same way those same terms are used for decimal networking speeds).

        • http://www.larsenconsulting.net Robert Larsen

          Accepted that the “new” terms have come about to try and clear up confusion — maybe I just haven’t seen them in widespread use as I work in telecoms rather than computing (which I moved away from longer ago than I care to remember). You’re probably right: an oldie like me needs to update my terminology…

    • http://etherealmind.com Greg Ferro

      Incorrect. See standards referenced in the article.

  • Brannen

    When referring to memory or storage, KB, MB,GB, TB etc refer to multiples of 1024.

    When referring to networking Kb, Mb, Gb, Tb etc refer to multiples of 1000. Notice the usage of the lower case b.

    Therefore 100MB 100Mb.

  • Brannen Taylor

    That’s really interesting.

    I have NEVER seen this “in the wild” (in real network documentation) . I think it would further confuse engineers from other disciplines to start using it.

    kibi-, mebi-, gibi-, tebi-, pebi-, exbi-

    • http://etherealmind.com Greg Ferro

      I use it all the time. Because I have to communicate with programmers and storage people who work in decimal binary or not as the case may be.

      Plus when I talk to service providers they use decimal binary. You really need to think about using it.

      • windexh8er

        This is actually a more clear example:


        It also has a good historical context to explain the “why”. Most people will look at you like you’re on crack (or think you have a speech impedement) though if you use this in most common situations. I have honestly never run across it in conversation for over 8 years working for over a dozen Fortune 50’s and army’s of programmers and network folk. Unfortunately that doesn’t make the misunderstanding correct.

        • http://etherealmind.com Greg Ferro

          Here’s how I see it.

          It’s computer people who have it wrong – kilo means one thousand. How the hell did we ever co-opt to the term 2^10 to mean a thousand of ANYTHING. Therefore it’s up to us to clearly define when using binary base maths. Its’ not reasonable to expect other people to change pre-existing engineering practice.

          We (computer people) need to change on this one, not the rest of the world.

          • http://www.larsenconsulting.net Robert Larsen

            “We … need to change …” — it’s a nice sentiment, but it ain’t gonne happen anytime soon. The vast, vast majority of IT professionals use kilo/mega/giga interchangably across multiple disciplines. For better or worse, those terms are pretty entrenched in the old grey matter.

          • http://etherealmind.com Greg Ferro

            The change starts with you and me then, are you in ?

          • http://www.larsenconsulting.net Robert Larsen

            I’ll certainly give it a go — if only to see what kind of reaction I get from my colleagues/customers… ha ha… 😉

          • Zeke

            I understand the confusion on this point, but not why we need different terms. When talking about bit / byte storage, kilo- is 1024. When talking about anything else, kilo- is 1000. Any remaining confusion must be due to missing context.

            In this article, 56 kilobits / -bytes per second is *probably* referring to some line speed or transfer speed. Thus, 56000 would be most correct. (If this were a block transfer speed of some drive, it would be 56 * 1024 = 57344).

            On the other hand, if we need new terms (we don’t), I agree that bit storage prefixes should change. SI says kilo = 10^3 and while a “bit” is not an SI unit, the prefixes are a long standing convention. These are the conventions described in the Wikipedia article.

  • http://aconaway.com Aaron

    The use of K- for “kilo” slays me. Ki- is fine, but K is degrees Kelvin.

  • Brannen Taylor

    Does anyone else differentiate with the B vs b or is that just me? I thought KB was Kilobyte (bits x 8 x 1024 Bytes) and Kb is Kilobits (bits x 1000) .

    • http://www.larsenconsulting.net Robert Larsen

      Yup — I’ve used that distinction as well in the past — but it’s very rare that I come across anyone else who uses it, so generally I don’t bother these days.

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