KB, MB, GHz, and All of That Stuff

In case you haven't noticed (fat chance), the computer biz is filled with words that start with "kilo" and "mega", and abbreviations like "K" and "M" and "G". These words and abbreviations don't represent "things". Rather, they represent numbers. Kind of like the old gangster movies where a bad guy would say fifty g's rather than fifty thousand dollars. Computer nerds use a different slang for numbers. But the idea is the same.

K. M, and G are Numbers

Let's start with just the numbers -- the K and M and G part. We'll talk about the "B" and "Hz" and stuff in a moment. Table 1 shows what the abbreviations mean, how they're often spoken, the approximate number each represents, and the way-too-trivial-a-difference-to-worry-about actual number each represents.

Abbreviation Stands for Spoken as Approximate # Actual #
K Kilo kay or killa 1,000 (a thousand) 1,024
M Mega meg 1,000,000 (a million) 1,048,576
G Giga gig or giga 1,000,000,000 (a billion) 1,073,741,824

Table 1

If you ignore the boring "actual" numbers, you'll see there's a simple pattern to it. Each time you go to from K to M to G, you stick another ,000 onto the end of the preceding number (also known as multiplying the previous number by a thousand), as you can see below:

So "K" means "thousand" or ",000", and "M" means "million" or ",000,000" and G means "billion" or ",000,000,000". Though maybe I should just shut up now before I make it sound more complicated than it is. Suffice it to say if you're gonna buy a used car, and it has 80K miles on it, then that means the car has 80,000 miles on it. If the car has 20M or 20G miles on it, don't buy it.

Tip: Just in case you're some kinda math brain who's wondering where the actual numbers come from, K=210, M=220, G=230.  (Yawn)

B is for Byte

Information in your head doesn't have any particular "size" to it. Just because Albert Einstein was a genius doesn't mean his head was the size of hot-air balloon or the Good Year blimp. His head was probably about the same size as anyone else's, give or take a couple inches. That's because the human brain stores information in some really weird abstract way that nobody understands.

Computers have no brains, and really don't store "information" the way a human brain does. In fact, computers don't really store "information" per se. Except in the sense that a book stores information -- as letters, numbers, pictures, and words. The information in a book has no meaning to the book. Likewise, the information in a computer has no "meaning" to the computer. Books and computers are a lot alike in that way -- they both can be used to store text, numbers and pictures. And they're also alike in that the text, pictures, and numbers inside have no "meaning" to either the book or the computer.

Anyway, the point is it takes a certain amount of "space" to store information outside of our brains. That's because the information needs to be stored as words, numbers, pictures, or something that takes up space. In a computer, the basic "unit" of measure is a byte, which is the amount of space it takes to store one character, like the letter "A" or an exclamation point (!). So it takes exactly three bytes to store the word "cat". It takes about 2,000 bytes to store one double-spaced page of typed text.

When you see an uppercase letter "B", that stands for "byte". So instead of saying it takes "three bytes" to to store the word "cat", I could have said it takes about 3B to store the word "cat". Likewise, I could have said it takes about 2,000B to store the a typed page of text. So now, given all you know about K and M and G, I bet you can figure out what KB. MB, and GB mean before you even peek at Table 2.

Abbreviation Stands for Approximate # (or) Actual #
KB Kilobyte 1,000 bytes A thousand bytes 1,024 bytes
MB Megabyte 1,000,000 bytes A million bytes 1,048,576 bytes
GB Gigabyte 1,000,000,000 bytes A billion bytes 1,073,741,824 bytes

Table 2

So before, when I was talking about a typed, double-spaced page of text taking up about "two thousand bytes" or "2,000B", I could have said it take about 2 KB to store that page of text. Often, the "B" is assumed, so it would be just as accurate for me to say it takes about 2 K to store that page.

If you already have files stored on your computer, and know how to get around in folders, you can see that every file has a size. You'll need to use the Details view (choose View > Details from the menu bar above the icons). Figure 1 shows an example where you can see the sizes of some pictures in a folder on my computer.

Figure 1

The first file in in Figure 1 has a size of 735 KB, (or roughly 735,000 bytes). The biggest file in that folder is 1,732 KB. That could actually be expressed as 1.7MB (because a megabyte is about 1,000 kilobytes). But Windows always shows the file sizes in kilobytes (KB) just to keep all the numbers on the same scale.

Of course, not all information in a computer is typed text. A computer can also store pictures, sound, and video. We generally refer to pictures, sound, and video as multimedia or media files. But like typed text, those files have sizes too. Table 3 provides some examples of multimedia files.

Example Size Or about...
The picture shown in Figure 1 61 KB 61,000 bytes
This entire Web page you're reading 125 KB 125,000 bytes
A 3-minute CD-quality song 3.5 MB 3,500 KB  or 3,500,000 bytes
1 minute of DVD-quality video with sound 11 MB 11,000 KB  or 11,000,000 bytes

Table 3

Exactly how much "stuff" you can get on a disk depends on the capacity of the disk. This is no different from the capacity of a container for water (e.g. cup, bucket, bathtub). But of course, we don't use "pint", "quart", "gallon" and such for describing disk capacities. We use (what else?), KB, MB, and GB.

There are lots of different "types" of disks out there. You've probably already heard of most of them -- floppy disks, CDs, DVDs, and of course the hard disk that lives inside every computer. Hard disks come in many different sizes., usually in the range of 20GB to 120GB. Table 4 lists the storage capacities of common types of disks. The column on the right describes the capacity in relation to the capacity of a floppy disk, just to give you some perspective on how greatly these capacities vary.

Disk type Capacity Equals this many floppy disks
Floppy disk 1.4 MB 1
CD 700 MB 700
DVD 4.7 GB 4,700
Hard disk 20 GB to 120 GB 20,000 to 120,000

Table 4

Tip: To see the storage capacity of your own computer's hard drive, and how much of that space is still available for storing more files, click here.


bps is for "bits per second"

The letters bps are short for bits per second. A byte (described earlier) is actually 8 bits. But that's not important. What's important is that unlike a byte, which is a measure of size, bps is a measure of speed. Simply stated, the higher the bps, the less time it takes. It's a lot like Miles Per Hour (MPH) in that sense. Think how long it would take to get from New York to California in a car going 55MPH. Now think how long that same trip would take in a jet going 700MPH. Simply stated, the higher the MPH (or bps), the less time it takes.

As a rule, we use bps as a measure of the speed of getting data from one computer to another across a network (including the Internet). And we use "K" for a thousand, "M" for a million, and "G" for a billion, as usual. Table 5 sums it all up. The fourth column shows some alternative abbreviations. The rule-of-thumb is that an uppercase B always stands for "bytes" while a lowercase "b" always stands for "bits per second".

Abbreviation Spoken Bits per Second (English) Alternative Abbreviations
Kbps Kilobits 1,000 Thousand Kb or Kbits
Mbps Megabits 1,000,000 Million Mb or Mbits
Gbps Gigabits 1,000,000,000 Billion Gb or Gbits

Table 5

The most common use for the bps measurements is in types of Internet accounts. To give you a sense of how the speeds relate to one another in terms of "wait time", Table 6 compares the amount of time it would take to download (copy) a 1MB file from a computer on the Internet to your own computer. (Since a byte is equal to 8 bits, a 1 MB file is roughly 8,000,000 bits.) Also, I'm using "Broadband" as a general term for Cable and DSL accounts, which are actually available in speeds ranging from about 256 Kbps to 1,000 Kbps. Note, too, that 1,000 Kbps is the same as 1 Mbps.


Account type Speed Bits per Second Time to download 1MB
Dial-up 56 Kbps 56,000 143 seconds
ISDN 128 Kbps 128,000 63 seconds
Broadband 1 Mbps 1,000,000 8 seconds
T1 1.5 Mbps 1,500,000 5 seconds

Table 6

Hz is for Hertz

The Hz abbreviation stands for Hertz, but has nothing to do with pain or car rentals. In this context, "Hertz" pays homage to a guy named Heinrich Rudolf Hertz who figured out that radio and electricity have frequencies that you can measure in cycles per seconds. But that's getting more technical (and boring) than we need to be.

The workhorse of your computer is its microprocessor - a little chip about the size of a toenail that can work at a pretty fast speed. Exactly how fast it can work is measured in terms of "instructions per second", which roughly corresponds to Hertz's idea of frequency. Of course, microprocessors can do thousands, millions, or billions of instructions per second. So that brings good old K, M, and G into the picture once again, as summarized in Table 7.

Abbreviation Stands for Cycles per Second That is...
KHz KiloHertz 1,000 Thousand
MHz MegaHertz 1,000,000 Million
GHz GigaHertz 1,000,000,000 Billion

Table 7

As is always the case with speed, "faster" means "less time waiting" for a human. The speed of the processor only affects "local tasks". It has nothing to do with how long it takes to get your e-mail or download stuff from the Internet. The speed of your Internet connection is all that matters there. The speed of your microprocessor has more to do with how long it takes to render changes to huge graphic images, or produce movies, or similar complex tasks that require a lot of internal calculations on the computer's part.

So there you have it. To summarize, K, M, and G are all abbreviations for numbers:

The letters that come after are either a measure of size or capacity, or a measure of speed, as follows:

You're becoming dangerously close to be a full-fledged computer nerd here...

Alan Simpson