• Megabit? Megabyte? Is there a difference?



    Marketing is a wonderful thing, isn't it?
    It's the art of giving you just enough information to make the wrong impression. There are marketers out there who willingly trade on what you think you know to make you buy something they don't even understand.

    Take the curious case of megabits, megabytes, and mebibytes. Mebibytes you say? What the frack is a mebibyte? Most people haven't heard of them so don't feel bad. Here's a way you can amaze your friends at the same time turn off telemarketers.



    Let's start with the basics. At the heart of it all is the bit. Bit is supposed to stand for "binary digit" but you know that's made up -- you know that the funny-cigarette-smoking computer guys in the 60s just came up with a food-oriented analogy for their numbers. A bit is either a 1 or a 0. It's on or off; as they used to say, it's got to be this or that. But a bit doesn't do a whole lot for you. It certainly isn't going to let you do a whole lot. In order to even show a single letter on the screen or a single note of music you need about 16 of them in a row.

    Back in the day, those hungry programmers decided to call a string of eight bits a byte. Eight bits got you just enough information to send a single letter, and so it was pretty useful. (For proof those people were using 'wacky weedus,' they also called four bits a nybble. What did they call two bits? Why, a shave and a haircut.)

    Even a byte doesn't do a whole lot for you. If one letter is one byte, you need several thousand of them for just this little article. That's where the metric system comes in. You remember the metric system... they tried to teach it to you in school but you thought you'd never need it.

    String 1,000,000 bytes together and you get a megabyte. (You know they wanted to call it a "chomp," you just know it.) String 1,000,000,000 bytes together and you get a gigabyte, which is enough for two movies or quite a few songs. But hey, you knew this.

    What you didn't realize is that while you were calling megabytes "megs" and gigabytes "gigs" your internet service provider has been waiting to confuse you with their own terminology. See, when networks started, speeds were measured in baud, meaning "bits of audio data." This wasn't the actual total of bits being transferred -- there were other sorts of bits in play that checked to make sure that nothing got messed up. So a line could be 380bps (bits per second) but actually give you only 300 baud. Well, since the bits per second number was higher, the marketers grabbed onto it. Maybe you remember dial up modems that measured speeds in Kbps (kilobits per second, or multiples of 1,000 bits per second.) Today's speeds are measured in Mbps,or megabits per second.

    OK... this is where the marketing comes in.

    See, speeds are measured in megabits per second but they know that you're trained to think in megabytes. See, if you want to transfer one megabyte, you actually need to transfer eight megabits. Not only that but when you're downloading, there's other data that hitches a ride to make sure that the data you want doesn't get corrupt. So the math gets even more confusing.

    Let's say you have a 25 megabit per second (25mbps) connection. You want to download a 25 megabyte file. How long does it take? if your first thought was "1 second" then the marketing people have done their job. In reality the fastest it could be would be 8 seconds (25 megabytes = 200 megabits) but with all the checking it is probably more like 12 seconds.

    When your internet service provider says you've got a "50 meg line" he's hoping you think that's a lot. In fact it means that the average HD movie will still download in roughly 20 minutes even if you're consistently getting top speed. That's fast, but it's not what you might have thought you were getting.

    Oh, what about mebibytes? We didn't forget them. A megabyte is 1,000,000 bytes but computers actually count in multiples of two. Megabytes make for good sales numbers but internally your computer is probably thinking in mebibytes. A mebibyte is 1,024,576 bytes. Most people ignore this convenient fact and then wonder why they can't fit the entire 56-hour Lord of the Rings saga onto a flash drive when the math says they should.

    So... the moral here is if someone comes up to you with a term like "meg" or "gig" make them explain it. You don't know if it's megabits, megabytes, or mebibytes, and the difference is pretty important.

    This article was inspired by: Your Internet Speed: Megabits vs. Megabytes | Ron Stauffer Blog

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    Comments 3 Comments
    1. HoTat2's Avatar
      HoTat2 -
      "Baud" means "bits of audio data?"

      Wow, after all this time I'd always thought it was the unit for code signaling speed named in honor of the French telegraph engineer Emile Baudot (1845-1903), the inventor of the Baudot code for telegraphy. 😀
    1. Stuart Sweet's Avatar
      Stuart Sweet -
      That's the first time I've heard that, I heard the other numerous times. Perhaps it's both.
    1. dsiebert's Avatar
      dsiebert -
      He's correct, at least about the signal speed not sure about the naming. Baud is the symbol rate, and is not the same as bps. 33.6 Kbps modems were 3429 baud, with 10 bit per symbol QAM coding and error correction.