Whats the difference between a MB and a Mb ?

By tonyhughes Hughes, in , posted: 23-Dec-2007 11:52

Not a lot, according to many. But in my line of work, its pretty crucial that whether the right language is used or not, that everyone is speaking the same language.

For example, I have a customer that always talks about his WAN speeds in megabytes per second, when he actually means megabits. I have made a couple of attempts to correct such mistakes, but at the end of the day, you can't let things like that become a barrier to doing business.

It is a bit of a worry though, when you see in the media, or online, or at seminars etc, people who deal with data devices and data connections for a living, and fail to understand the fundamental differences between the different terminology.

For example:

If we put in a 10 megabit circuit for a client, the accepted symbol or acronym, is 10Mbps (or 10Mb). Yet the number of people I see writing it as 10MBps (or 10MB) is disastrously common.

There are 8 bits that go to make up a byte, so 10Mb != 10MB.

Kilobits (Kb) and Kilobytes (KB) are again, very different. (If you have dialup internet, chances are you have a 56Kbps modem - note the lower case 'b' to indicate bits not bytes.

http://en.wikipedia.org/wiki/Bit_rate
http://www.oempcworld.com/support/MB_vs_Mbits.htm
http://www.ists.dartmouth.edu/classroom/crs/ethp_mb.php
http://www.dewassoc.com/performance/memory/MB_vs_Mb.htm
Google search for MB vs Mb



Other related posts:
Kiwibank to offer personal finance via GE Money
TiVo in New Zealand - Do You Want One?
A new lease on life for a Squier California Strat








Comment by grant_k, on 23-Dec-2007 12:29

@Tony:  "Kilobits (Kb) and Kilobytes (KB) are again, very different. (If you have dialup internet, chances are you have a 56Kbps modem"

Actually Tony, just to be a total pedant, I will pull you up on a minor infringement of the rules here:

The SI symbol k is short for kilo, meaning 1000, and should be written in lower case, not upper case.

Strictly speaking, if you write the symbol K in the SI system, it means Kelvin, a measurement of Absolute Temperature, as opposed to C which is short for Celcius, or Temperature relative to the freezing point of water.

/me climbs down from soapbox


Comment by sbiddle, on 23-Dec-2007 12:39

If you look at a lot of packing it's very common to see kg (kilogram) expressed as either KG or Kg, both of which are incorrect.


Author's note by tonyhughes, on 23-Dec-2007 13:21

oops yes, you are of course right about big K vs. little k, but the difference doesn't have a bearing on data rates or sizes :-P


Comment by KiwiOverseas66, on 23-Dec-2007 20:33

lol - I've done exactly the same thing in terms of trying to explain the difference to workmates and friends! I think its one of those things that will never change - and eventually the misconception enters everyday language and becomes the norm. Good indicator, though, when you're in a showroom talking to the local staff as to whether or not they know what they're selling.

A bit like my favourite bug bear "modem".  If its a digital signal throughout - then the device on the end of your broadband doesn't modulate - demodulate - therefore it isn't a modem (and yes I that's how its marketed and branded - but that isn't the physics of the situation). ;-)


Comment by TinyTim, on 27-Dec-2007 20:44

@grant_k - if you're quoting SI then more important is the use of the letter 'p' to mean 'per' when in SI it means pico.

How about using kb/s (as per the IEEE)?


Comment by Bob, on 8-Jul-2009 01:16

firstly well done tony on shooting down the totaly randomly unrilated comment made by grant_k secondly (although i am compltely at peace with the differences) do we know the reason why it all started and people didnt just work with bits, Kb, Mb, etc... why did someone bring in the bytes side of it??? instead of 1TB they could of said 8Tb (thats how i would sell a HDD on eBay ;) *last point, this line didnt make sence... "There are 8 bits that go to make up a byte, so 10Mb != 10MB." shouldnt that read, ...~so 10Mb != 1.25MB.*


Comment by hfinity, on 20-Jul-2009 12:14

"shouldnt that read, ...~so 10Mb != 1.25MB.*" Eh Bob, no. 10Mb = 1.25MB but 10Mb != 10MB and 10Mb != 100MB. See the difference or do you not know what != is?


Comment by Larry, on 28-Aug-2009 08:54

The symbol "!" is the symbol for factorial in mathematics, so "n!" would give the factorial for the variable "n". If you input any number on the calculator followed by the symbol "n!" you would be taking the factorial of that number. And in case you are not familiar with how to calculate factorial, factorial involves multiplying together each successive integer, beginning with 1, leading to that integer. For example: 1! = 1 * 1 = 1 2! = 1 * 2 = 2 3! = 1 * 2 * 3 = 6 4! = 1 * 2 * 3 * 4 = 24 5! = 1 * 2 * 3 * 4 * 5 = 120 etc...


Comment by Larry, on 28-Aug-2009 08:57

The symbol "!" is the symbol for factorial in mathematics, so "n!" would give the factorial for the variable "n". If you input any number on the calculator followed by the symbol "n!" you would be taking the factorial of that number. And in case you are not familiar with how to calculate factorial, factorial involves multiplying together each successive integer, beginning with 1, leading to that integer. For example: 1! = 1 * 1 = 1 2! = 1 * 2 = 2 3! = 1 * 2 * 3 = 6 4! = 1 * 2 * 3 * 4 = 24 5! = 1 * 2 * 3 * 4 * 5 = 120 etc...


Comment by Tajdar, on 8-Jan-2010 04:38

Thanx Tony . It was really bugging me that Having a 1MB (Which is actually 1 Mb/s ) connection was not going above 100 KBp/s. But now i get it, the services providers uses misconception as a MARKETING tactic. Thanks again.


Comment by Garry, on 18-Aug-2012 10:17

...... 8-) .... wow ... never have i seen a quality debate go so abstract as to the real reason as to why it started ?? must admit, i cant stop laughing ... brilliant .. totaly brilliant. btw, i still have to question myself from time to time as to which is the larger/greater of the two and remenber that Big means better and that does it for me. still laughing ... ;-)


Comment by Dave P, on 16-Jul-2013 19:50

Great discussion and one that has irritated me for a long time. I've been in IT since the days when real modems were measured in baud rates :0) One last pedantic point - the K in the network line speed , doesn't actually mean 1,000. It is one kilobyte or kilobit which is actual 1,024 bytes or bits. Just as Mega/bit/byte doesn't isn't exactly a million


Comment by Will, on 11-Aug-2013 18:08

Seriously Tony you are right but why use != in your explanation? Did you think only programmers and alike were going to be looking up the difference between bits and bytes? Why does everyone have to be so clever? Did it not occur to you that people who aren't in the know are most likely to research this topic?I am sure you noticed people commenting on it - what a shock!


Comment by Gerard Perreault, on 16-Oct-2015 08:10

I suppose we can agree to disagree, but having only 26 letters available, for a total of 52 if you distinguish between uppercase and lowercase, it would seem that a one letter abbreviation should only be meaningful in the context of the discussion. In this case, we you are talking about temperatures a lowercase k would represent something different than a lowercase k in computing, or radio frequencies. Unfortunately, even withing the computing context, I have noticed that manufacturers then to pick the nomenclature that best favors their equipment. So, instead of being clear about something's performance, as in 500Mbps, they will use 500Mb, hoping that they less knowledgeable client will confuse it with 500MB (or they will outright indicate 500MB relying on the fact that in most cases there isn't anyone to enforce the nomenclature used).For that matter, they started doing that when the Mega symbol first appeared. When K in computing started to be used it meant not 1,000 but 1,024. A mega byte (MB) was 1024x1024 (1,048,576 bytes) but they soon notices than 480MB (503,316,480 bytes) could be sold as a 500MB device if you took the M to represent not the original 1024x1024, but 1000x1000.And of course this issue didn't stop with MB. A Giga byte should be 1,073,741,824 bytes, and a Tetra byte 1,099,511,627,776 bytes. So, when not calculated as the technology originally dictated, for every TB we lose about 100gB (I decided to use lowercase g to indicate a value which is a multiple of 1,000 instead of 1,024).So, what are we to conclude other than, the market drives, but the true scientist continue to use the correct terms. For me, KMGT are 1,024 or a multiple of it.BTW: What comes after T?Thanks.


Add a comment

Please note: comments that are inappropriate or promotional in nature will be deleted. E-mail addresses are not displayed, but you must enter a valid e-mail address to confirm your comments.

Are you a registered Geekzone user? Login to have the fields below automatically filled in for you and to enable links in comments. If you have (or qualify to have) a Geekzone Blog then your comment will be automatically confirmed and shown in this blog post.

Your name:

Your e-mail:

Your webpage:



Subscribe To My RSS Feed