Memory Sizes Explained – Gigabytes, Terabytes & Petabytes in Layman’s Terms

Data Sizes For Laymen Intro   Memory Sizes Explained   Gigabytes, Terabytes & Petabytes in Laymans TermsIt’s easy to see that 500 gigabytes is more than 100 gigabytes. It’s also easy to see that 1 terabyte is larger than 1 gigabyte and that is larger than 1 megabyte. But these are all abstract terms and names. We can visualize 1 inch or 1 meter or 1 mile, but how can we visualize 1 gigabyte? 1 terabyte? 1 petabyte?

Our technology has progressed very far in the last decade or so, and with so much memory space available, it’s hard to really appreciate how much data capacity we have. Keep reading to find out just how big a gigabyte, a terabyte, and a petabyte are.

The Gigabyte = 1,024 Megabytes

data layman gigabyte   Memory Sizes Explained   Gigabytes, Terabytes & Petabytes in Laymans Terms

We start with the lowly “byte”. In simplest terms, 1 byte is the amount of data needed to store 1 character (letter). If the average word is 6 characters long, then the average word is 6 bytes. For a 500-word essay, that’s 3,000 bytes.

You need 1,024 bytes to have 1 kilobyte (KB). You may recognize the “kilo” prefix from similar terms like “kilometer” and “kilogram”, both of which mean “a thousand meters” and “a thousand grams” respectively. But because of the way computers are designed, the number 1,024 is used in place of 1,000.

So a 500-word essay is 3,000 bytes, or 2.92 KB. A 200,000-word novel, then, would require 1,172 KB, or 1.14 megabytes (MB). The complete works of Shakespeare would take up approximately 5 MB of space in plain text format. 5 MB is also the average amount of space required for a 5-minute MP3 file.

A gigabyte (GB) is 1,024 MB. That’s equivalent to 10 yards of books standing side by side. That’s 200 MP3 songs running at 5 minutes each. That’s a little bigger than the size of a feature film at standard definition. But most of us are already familiar with the term “gigabyte”. So what comes next?

The Terabyte = 1,024 Gigabytes

data layman terabyte   Memory Sizes Explained   Gigabytes, Terabytes & Petabytes in Laymans Terms

For a long time, hard drives were measured in GB. My 6-year-old laptop has an 80GB hard drive. My current desktop computer has a 300GB hard drive. But in the past few years, hardware developers have come out with 1- and 2-terabyte (TB) hard drives. How big of an improvement is this?

Well, 1 TB = 1,024 GB = 1,048,576 MB = 1,073,741,824 KB = 1,099,511,627,776 bytes. In other words, a 1 TB hard drive has the capacity to hold a trillion bytes. That’s a far step up from floppy disks that only held thousands of bytes.

Do you remember CD-ROMs? Way back before mp3 players and iPods and smartphones, music used to be sold and purchased on plastic laser-etched circles that would spin. These discs were large enough to hold 700 MB. How does that compare to the 1 TB hard drives of today?

You would need approximately 1,500 CD-ROMs to match the capacity of a 1 TB hard drive. Now, let’s say that the dimensions of a CD case are 142 mm x 125 mm x 8 mm (yes, I measured). If you stacked 1,500 CD cases on top of one another – and kept it from toppling over – it would reach a height of 12 meters, or 39 feet. You can enjoy all of that memory space within a compact metallic storage device now. Impressive.

The Petabyte = 1,024 Terabytes

data layman petabyte   Memory Sizes Explained   Gigabytes, Terabytes & Petabytes in Laymans Terms

And finally, we arrive at the newest data size that is slowly but surely becoming a norm in regular conversation – the petabyte (PB). The human brain reportedly has the ability to store about 2.5 petabytes of memories. The Large Hadron Collider generates around 15 petabytes of data every year. AT&T transfers approximately 20 petabytes of data through its network every day.

When we talk about data capacities in this range, it becomes hard to visualize just how grand of a scale we’re talking about. If 1 TB is a trillion bytes, then 1 PB is a quadrillion bytes. In scientific notation, that’s 1015! Even as I write this, I’m having a hard time comprehending just how big that is.

Our Milky Way Galaxy is home to approximately 2 hundred billion stars. If each individual star was a single byte, then we would need 5,000 Milky Way Galaxies to reach 1 PB of data.

Or how about television? If we were to count using standard definition TV episodes, then 1 PB would amount to around 10,000 hours of TV programming. If you watched all of those episodes without ever stopping – not even to eat, drink, or sleep – it would take you 2 non-stop years to watch it all.

This is the kind of capacity we have for data storage today. Quadrillions of bytes passing through our network cables right under our noses every second. Only 10 years ago, a single CD would hold maybe 20 MP3 songs; today, we can load up our HDDs and SSDs with thousands and thousands of songs easily.

Technology has advanced in great ways and data storage is no exception. I hope this article has given you a glimpse of just how far we’ve come.

Image Credit: Data Network Image Via Shutterstock, Infographic by

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Roman Vávra

finally, I get it, thanks a log! :)

Roman Vávra

*a lot


For a long HDs were measured mega bytes. My first computer with a hard drive had a 40 meg HD and 2 meg of memory, what a screamer, I was the every of everyone at work.

Joel Lee

Those were the days! Though my first computer had a 200 MB hard drive. I got so mad because I couldn’t install Starcraft on it. :D


thanks nice read.

Hope MS windows is now able to read 4Tb drives


Windows Vista and higher can read drives larger than 2TB *as long as your motherboard has EFI*

Larger drives require a GUID Partition Table which requires EFI (Extended Firmware Interface, a replacement for the aging BIOS).


how do i know if my mb has EFI?

I had bought a 3Tb ext. WD but Win7 failed to see anything beyond 2Tb.


External HDs aren’t handled by the motherboard (unless they’re eSATA); FireWire and USB 2.0 and 3.0 drives are handled by a controller chip on the IDE-to-USB or SATA-to-USB “bridge” that makes them USB or FireWire compatible.

An EFI/UEFI firmware won’t have a BIOS; from what I know, it will use a bootloader to install 200MB or more of system utilities into a hidden partition on your C: drive, which will load a GUI (graphics and mouse) utility to set up the motherboard.

Here’s a YouTube video showing off an ASUS EFI (Intel) system:


I think ur wrong 1 byte = 8 bits .1 bit =1 or 0.

Joel Lee

You’re right, but I’m not sure where in the article I said otherwise? 1 byte is indeed 8 bits.


yes RAM you are correct .
i bit = 1 char.


yes RAM you are correct .
i bit = 1 char.


I think u r wrong . 1 byte=8 bits. 1 bit= 1 or 0

George. W

Then you get your Exabyte, Zettabyte and then Yottabyte, although there is nothing in existence that equals a yottabyte, seeing as the entire contents of the internet is around 600 Exabytes.

Joel Lee

600 Exabytes? Wow. I’ll bet it takes no time at all to double that and reach our first international Yottabyte!


I read somewhere that internet grows by a speed of 40 odd exabytes per month! It’ll double in no time….


Could you give me a source to this statement? I’m really curious to read more about the growth and the size of the internet. Thanks!

Daniel Tanner

In another perspective on TRILLION:

Trillion = 1,000,000,000,000.
The country has not existed for a trillion seconds.
Western civilization has not been around a trillion seconds.
One trillion seconds ago – 31,688 years – Neanderthals stalked the plains of Europe.

Joel Lee

Eesh, that’s a long time. Really puts it all in perspective. Thanks!


That’s a really interesting approach. Thanks for sharing.

Alex Shen

You might wanna correct this bit in the article:
‘If 1 TB is a trillion bytes, then 1 PB is a quadrillion bytes. In scientific notation, that’s 1015!’ to ’10^15′- at first (skim) read I didn’t understand what you meant, then i realised. Great article, I tend to get confused past terabyte. Looking forward to shelling out for my first petabyte HDD in the near future… (not)

Joel Lee

Thanks for the catch! You are absolutely right. It seems that pasting from Word into WordPress isn’t entirely foolproof. :(


The meaning of the prefixes kilo, mega, giga, tera etc. is defined by the Système international d’unitĂ©s (SI) and no amount of misuse can change that.

1 kilobyte = 10^3 or 1,000 bytes; 1 kibibyte = 2^10 or 1024 bytes
1 megabyte = 10^6 or 1,000,000 bytes; 1 mebibyte = 2^20 or 1,048,576 bytes
1 gigabyte = 10^9 or 1,000,000,000 bytes; 1 gibibyte = 2^30 or 1,073,741,824 bytes
1 terabyte = 10^12 or 1,000,000,000,000 bytes; 1 tebibyte = 2^40 or 1,099,511,627,776 bytes

Joel Lee

You are technically correct, but walk into a Best Buy and ask for a 500 gibibyte hard drive and you’re going to get some wacky looks. The terms have become so entrenched in the common world of computers that the SI prefixes are interchangeable with the true prefixes. Languages evolve!

The 24

I maintain that a Gigabyte is NOT 1024 Megabytes. It is 1000 Megabytes. In the same way, A Terabyte is not 1024 Gigabytes, but 1000 Gigabytes.

Both ‘giga’ and ‘mega’ along with ‘kilo’ and ‘tera’ are metric prefixes which means they increase by scale factors of 1000.

However, 1024 Bytes is a Kibibyte, and 1024 Kibibytes is a Mebibyte. Therefore 1024 Mebibytes is a Gibibyte and so on.

Of course in this instance, ‘kilo’ and ‘kibi’ as well as ‘mega’ and ‘mebi’ etc. are largely used interchangeably, which I think is the entire reason people have become confused. For example, my grandmother asked me why her supposed 500 GB hard drive only registered as about 466 GB when she checked the properties on her C: drive.

The problem is humans use metric whereas computers use binary. Although salespersons will use whichever number is larger. Perhaps we should stop using the binary prefixes even though it is theoretically the most important, and use only metric i.e. 1000 bytes is a Kilobyte and 1,000,000 bytes is a Megabyte. 1024 seems an odd number to use, and increasing by a factor of 1000 is much more intuitive may help alleviate some of the confusion that arises.

Of course, I may be in the minority with my opinions.

Joel Lee

Like Geoff, you are technically correct, but the terms are so interchangeably used already. Maybe the world of computers should move away from prefixes completely and rely entirely on the abbreviations KB, MB, GB, etc. Then 1 GB would really be 1,024 MB in all cases. :)


If you want a shorthand for the non-SI units, the standard is to put an “i” in the shorthand, such as Kibibyte would be KiB etc.

Tug Ricks

I think I’ll stick with political science… :)

Ashwin Ramesh

Cool description! Esp. the petabyte :) Now I understand memory sizes!

Joel Lee

Glad it helped! :)

Mani Ahmed

Its been a year since i started wondering about the next word after tera byte, a computer user since the time when computers came with 64Kb of RAM and virtually NO HARD DRIVE (commodore 64 and 128 came with tape drives for storage and system was someone burnt IN the hard ware ROM) and then 512kb of RAM and 80Mb of hard drive (80×286 series) i have seen 3 generations of bytes, the kilo, mega and giga, yet to enter the tera … and now petabyte!

thanks !

Nehad Hussain

When can i have thousands of TB’s at my disposable??

Joel Lee

That’s still a few years away, I’m afraid. But just sit tight and it’ll arrive faster than you know. ;)


In the beginning.. I think There is some mistake .. .
you write something like this .. under heading

The Gigabyte = 1,024 Megabytes

# 1 byte is the amount of data needed to store 1 character (letter)

i think That is 1 character = 1 bit

not the 1 byte = 1 char. as you written.

Thank you.

Joel Lee

Sorry, you are incorrect. Please read Scutterman’s reply below to see why.


Several people have said that one character is actually one bit, but this is incorrect.

One bit holds a 1 or a 0. Commonly, a combination of 8 of these bits (one byte) is used to represent one letter or symbol on the screen. This gives a total of 256 possible characters that can be represented. Different encoding may take up more that one byte in order to display a wider range.
The representation of one ASCII or unicode character usually takes up one byte, though it can be more depending on the encoding.

If you attempted to store characters in bits, you’d only have two possible characters. Whether you treat these as 1 and 0, on and off, true and false, or yes or no, you still only ever get two possibilities.

Joel Lee

Thanks. You saved me from having to type out a long response of my own. :)

Mike Vaz

I can’t wait add more RAM to my brain :P

Dee Wheat

You would be amazed….not so many years ago I went to my kid’s high school and cleaned up their entire computer lab, which was filled with 2 gig hard drive desktops with so little RAM that I was astonished that they even functioned. Another thing that astonished me was that the local computer shop was charging $300 to change those 2 gig hard drives!!!!! This was not in the dark ages, but rather in 2004! That’s one reason I love the MUO cheats that address hardware issues. It would irritate the crap out of me to have to pay some kid who is barely potty trained $80 an hour to pull covers and swap parts!

Praveen pandey

here is the full list
1,0 = 1 bit
8bit=1 byte
1024 byte=1 KB
1024 KB= 1 MB
1024 MB=1 GB
1024 GB= 1 TB
1024 TB= 1 PB


nice ty!!


hey guys
Counting is still ON……..
Petabyte ( 10^15)
Exabyte ( 10^18)
Zetabyte ( 10^21)
Yottabyte ( 10^24)

Seishun Kyosoukyoku

Thanks for Share …


Wow! That’s a lot of data to process! :p

josemon maliakal

very useful info


I have been wanting this info for a very long time ty ty!!!

Evan Spangler

This is neat, and really informative. It’s neat to see things like how much data Google goes through every day.

Dos Moonen

Please learn people the correct things. 1 KB = 10^3 bytes = 1000 bytes. Kilo stands for 1000. 1 KiB = 2^10 bytes = 1024 bytes. KB stands for KiliByte, KiB stands for KibiByte.

This goes on for MegaByte (10^6 bytes), GigaByte (10^9 bytes), TeraByte (10^12 bytes) etc. and MebiByte (2^20 bytes), GibyByte (2^30 bytes), TebiByte (2^40 bytes).

Thank you for feeding the confusion -.-

Faisal Ahmed

“The human brain reportedly has the ability to store about 2.5 petabytes of memories.”
I wish I could add some “RAM” on my memory!!!