what are kilobytes, megabytes, gigabytes & terabytes?

If you're using a computer in any way at all, you just have to bump into Kilobytes, Megabytes and Gigabytes.

But what exactly are? And how do they relate to each other.?

Well, in short, they are simply a way of measuring either, how much data we've got, or, how much space we've got to store that data.

Imagine you've got two litres of water, you're gonna need a jug or bucket of at least 2-litre capacity, to store that water in. That's obvious, right.

In exactly the same way, if you've got 2 Gigabytes of data, then your gonna need a device with at least 2 Gigabytes of storage capacity.

Home » Computer Guides » What are Kilobytes Megabytes Gigabytes

bits and bytes.

Every file on your PC (every document, picture, piece of music, video etc) has a size. They require space to be stored.

And it's the way in which computers store these files that we need to measure.

Before we can get a grip on what exactly Kilobytes (KB), Megabytes (MB) and Gigabytes (GB) are, we need to know where they come from.

Our story starts with the humble Bit.

So what's a Bit I hear you shout.

Well most of us know that computers store and transmit data as ones and zeros.

We might not understand exactly how that happens, but we know they do.

Well, a Bit is a single one or a single zero.

Rather than keep saying ones & zeros, we can just say Bits.

a bit.

So What's A Byte?

You'll wish you never asked, a Byte is 8 Bits.

So 8 Bits is 1 Byte.

Or put another way, 8 ones & zeros is 1 Byte.

What we're doing is counting the number of ones & zeros. The number of Bits.

And really, that's all Kilobytes (KB), Megabytes (MB) and Gigabytes (GB) are doing. They're just counting the number of ones and zeros, as you'll see.

8 bits are 1 byte.

Now I know that changing at 8 is strange, why not change at 10, it'd be much easier.

But that's only if your counting in the decimal system, which we humans do.

Computers, on the other hand, count in the binary system, and to them, changing at 8 makes perfect sense.

But don't worry about that. We just need to know that when you've got 8 Bits, you can call them 1 Byte.

You can try this for yourself.

Open Notepad on your computer, then type just a single letter or number. Nothing else.

Save the file onto your Desktop, calling it "test file".

If your not sure how to do this, take a look at How to Save a File on a PC

type the letter "a".

Find the "test file" on your Desktop, right-click it, then left-click PROPERTIES on the menu that appears.

You'll see that it is 1 Byte.

That's because every character that you can type into Notepad is represented by 8 bits, or 8 ones & zeros, or 1 Byte.

For instance

the letter "a" is 01100001
the letter "b" is 01100010
the letter "c" is 01100011

1 letter = 1 byte.

Think of how Morse code works, you know Dots and Dashes.

The letter "a" is dot dash

the letter "b" is dash dot dot dot

the letter "c" is dash dot dash dot.

What Notepad is doing is very similar, except it's using ones & zeros instead of dots & dashes.

dot dot dash.

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kilobytes & megabytes.

OK, so far we've got 8 bits to the byte. And 1 byte is a single letter in Notepad. Just one letter.

So a single byte is a tiny amount of data. It doesn't tell you a lot.

To get anything meaningful, we'd need lots and lots of bytes.

So in Notepad, we're using 1 byte (8 Bits or 8 ones & zeros) to represent each and every letter and number, every punctuation mark and every press of the space bar.

How many Bytes would we use in a 5000-word essay or report?

Remember, it's 1 Byte for every letter, not every word.

You can see that the number of Bytes will be huge.

What we need is a way to bring the numbers down to a manageable size.

1 kilobyte.

In the metric system, whenever you reach 1000, you add the word Kilo. 1000 metres becomes 1 Kilo-metre, 1000 litres becomes 1 Kilo-litre

So 1000 Bytes could become 1 Kilo-Byte. It would make sense, wouldn't it?

So let's take a moment to consider exactly what 1 Kilobyte is.

Now, remember that we're counting the number of Bits, the number of ones & zeros.

So 1 KB is 1000 Bytes, and 1 Byte is 8 Bits.

So 1 Kilobyte is 8000 Bits, or 8000 ones & zeros.

When we reach a thousand Kilobytes, we need to change Kilo for something else, but what?

Well, how about Mega. Everyone knows Mega means big, as in mega-deal, mega-rich etc.

Also, Mega means 1 million in Greek.

And 1 Megabyte is 1 million Bytes.

The average 3-minute pop song weighs in at around 40 to 50 Megabytes.

Here we go,

1 Megabyte is 1000 Kilobytes. 1 Kilobyte is 1000 Bytes and 1 Byte is 8 bits (or 8 ones & zeros).

So 1 Megabyte is 1000 x 1000 x 8 = 8 million bits or 8 million ones & zeros.

Taking a pop song at around 40 MB, then that works out to be, 320,000,000 bits. That's a lot of 1s and 0s

You can see why we have to reduce the sheer size of the numbers.

gigabytes & terabytes.

There was a time when a Megabyte was considered to be a huge amount of data. After all, it's 8 million ones & zeros.

But not any more. Today, a Megabyte is a relatively small amount of data. So where do we go next?

We've gone from Bits to Bytes (which are tiny), to Kilobytes (which are very small), to Megabytes (which are small, but significant).

In mathematics, a Giga or Giga symbol means 1 billion.

You can see where this is going.

A Gigabyte is 1000 Megabytes. Which works out to be 1 billion Bytes or 8 billion bits. 8 billion ones & zeros.

A single layer DVD can hold 4.7 Gigabytes of data.

Which is 37,600,000,000 ones & zeros.

Or 1 DVD movie.

fancy a movie?

And so it goes on.

Gigabytes were considered to be so huge an amount of data, that no-one really thought we'd need to go past them.

But that didn't last long. So what's next.

After Gigabytes, we change to Terabytes.

1 Terabyte is equal to 1000 Gigabytes.

That's the equivalent of over 200 standard DVD's.

Modern computer hard drives are generally measured in either Gigabytes or Terabytes.

And there are more. After Terabytes, the next one is a Petabyte, followed by Exabytes, then Zettabytes and then Yottabyte.

And by the time you read this, there may even be more because the sheer amount of data that we're storing on computers is growing out of control.


megabytes, gigabytes & terabytes.

Megabytes (MB), Gigabytes (GB) and Terabytes (TB) are the only sizes you'll need to know about at home. For now.

Bits, Bytes and even Kilobytes are so small that, for the most part, you can simply ignore them. You know about them, and you know what they are, you know they exist.

But the three to concentrate on, the three that you'll use on your home PC, are Megabytes, Gigabytes and Terabytes.

trying to remember MB, GB, & TB.

Trying to remember Megabytes, Gigabytes and Terabytes isn't that easy if you're not using them regularly.

The words are strange words to our ears. They're not normal words.

And so trying to remember them, and their relationship to each other is difficult. It's almost a new language.

Try explaining the Imperial measurement system to someone brought up on the Metric system, or vice versa and you'll see what I mean. It begins to sound like gobbledegook.

So let's see if we can break it down a little.

First, we've got a thousand. The words change at one thousand. So Mega becomes Giga at one thousand.

Now one thousand is easy, we're used to using a thousand. It's nothing difficult. We can do a thousand.

So what we need to remember is that a Mega, goes into a Giga, and a Giga goes into a Tera.

Megabyte to Gigabyte to Terabyte. And each time the change happens at 1000.

megabyte in gigabyte in terabyte.

is it really 1000, or is it 1024?

At every stage so far, I've said that when you reach 1000 you change up.

So 1000 Kilobytes becomes a Megabyte, 1000 Megabytes becomes a Gigabyte and 1000 Gigabytes becomes a Terabyte.

But if you search the net, or read through some textbooks, you'll be told that actually, you change up when you reach 1024, not 1000.

So which is it? Well, that depends on who you're talking to.

A human or a computer.

For us humans, 1000 is a nice number. You can easily add or subtract 1000 in your head, no need for pen and paper.

You can even multiply and divide by 1000 without too much trouble.

1000 is a good number to work with.

But that's because we count in the decimal system.

multipling by 1000 is easy.

One thousand is a good number because it's a one and then a few zeros, 1000. It's nice and neat. There are no straggly numbers on the end to deal with.

Computers, on the other hand, count in the binary system.

Numbers look very different in binary. For a start, you can only have 1's and 0's.

Incidentally, that's why we refer to Bits as ones and zeros.

Let's take that nice number 1000. Looks good to me and you. We can work with that.

But in binary it looks very different. In binary, it looks like this - 01111101000

Not such an easy number now is it? Actually, it's a bit of a mess.

But guess what 1024 looks like in binary - 10000000000

Now I know there's a lot of noughts, but all the same, you can see it's a much easier number to work with.

Here are my thoughts on the matter. Whenever you're counting your Kilobytes, Megabytes, Gigabytes and Terabytes, always change up at 1000.

Don't worry about the 24 at the end. That's for the computer to worry about.

info icon

Explaining how the Binary system works is way over my head. But if you'd like more information, you could try here https://en.wikipedia.org/wiki/Binary_number

and finally, KB, MB, GB and TB.

When your writing the short form of Kilobytes, Megabytes, Gigabytes and Terabytes, always write it with CAPITAL letters.


The capital "B" represents Bytes.

Kb, Mb, Gb, and Tb are not the same. The lower case "b" represents bits.

Kb = Kilobits, Mb = Megabits, Gb = Gigabits and Tb = Terabits.


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