Technology Explained Web Culture

Memory Sizes Explained: Gigabytes, Terabytes, and Petabytes in Context

Joel Lee 14-08-2012

Updated by Gavin Phillips on 04/14/2017


It’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

memory sizes explained

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 How to Reduce Video File Size Without Losing Quality Is your video file taking up way too much space? It's time to encode, compress, and tweak it so that it shrinks in size without losing any noticeable quality. Read More . But most of us are already familiar with the term “gigabyte”. So what comes next?

The Terabyte = 1,024 Gigabytes

computer memory sizes explained

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

memory sizes explained

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 10 Video Sites That Are Better Than YouTube Here are some great alternative video sites to YouTube, although the "better than" is obviously open to debate. Read More . 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 25 Amazingly Interesting YouTube Facts You Should Know There's a lot you probably don't know about YouTube, so here are some amazingly interesting YouTube facts to check out. Read More .

Look How Far We’ve Come

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. For more, check out a comparison of megabits and megabytes Megabit (Mb) vs. Megabyte (MB): We Make It Less Confusing Confused about the difference between megabits and megabytes? One is for storage, the other for speed. But which is which? Read More .

Image Credit: Dooder via, Infographic by

Explore more about: Computer Memory, Hard Drive, Storage.

Whatsapp Pinterest

Enjoyed this article? Stay informed by joining our newsletter!

Enter your Email

Leave a Reply

Your email address will not be published. Required fields are marked *

  1. Karen C.
    March 30, 2018 at 11:50 am

    We were just looking at computers ( wondering what to buy) and I found this article! Thank you SO much for explaining everything! ( especially for this non-tech level 60 person ?)

  2. peg
    February 25, 2017 at 12:59 pm

    Very interesting, the comparison to everyday items finally helped me understand what is available. I am shopping right now for a new lap top and this was great
    Thank you

  3. Shannon Smith
    February 24, 2017 at 11:17 am

    This was super helpful!

  4. sean
    January 20, 2017 at 3:26 am

    thx for the explaination. im doing a school project and i have 2 annotate 2 websites i used. I need 2 know the publisher/sponsor

  5. mr. handsome
    December 6, 2016 at 4:13 pm

    OMG my dad told me about bytes but he did not tell me a petabyte is so much data!!!!!

  6. shark
    December 1, 2016 at 1:59 am

    I was in the day of floppy disks and now how good is this

  7. albert
    September 14, 2016 at 6:57 am

    thank you for the clear explanation.

    • Joel Lee
      September 20, 2016 at 12:38 am

      Glad you found it useful Albert! If you have any questions, please feel free to ask. Thanks.

    • Lewis
      December 4, 2016 at 3:07 am

      My 1st computer from Tandy (Radio Shack)had a whopping memory of I think 23 kb.!

      • mr. handsome
        December 6, 2016 at 4:28 pm

        ha ha

      • mr. handsome
        December 7, 2016 at 4:18 pm


  8. aaron
    July 29, 2016 at 4:11 pm

    Damn he really knows his shit

    • Joel Lee
      July 29, 2016 at 8:07 pm

      Thanks aaron! Glad you found it informative.

  9. Anonymous
    July 8, 2016 at 1:23 pm

    I don’t like to argue but 1000 bytes is a kilobyte, not 1024. Windows displays this differently, but the correct term for 1024 is kibibyte, mebibyte, etc. Search how many megabytes in a gigabyte on google. Search 1 megabyte to mebibytes

    • RZ
      September 13, 2016 at 11:52 am

      ty! :) 2^10 10^2

  10. Gabi
    June 22, 2016 at 8:25 pm

    Thank you for the brake down.

    • Joel Lee
      June 24, 2016 at 1:57 am

      No problem, Gabi!

  11. Smccool
    June 10, 2016 at 10:55 pm

    Wow, broke down in a way that was easy for me.

    • Joel Lee
      June 14, 2016 at 3:55 am

      Great! Glad it was helpful for you, Smccool. :)

  12. David
    April 22, 2016 at 3:58 pm

    This helped me out so much. Great examples!

    • Joel Lee
      April 23, 2016 at 10:50 pm

      Awesome! I'm glad it was useful for you, David. Thanks. :)

      • David
        April 23, 2016 at 10:54 pm

        No problem
        : P

  13. nopoop
    February 3, 2016 at 12:41 pm

    Amazing - great article

  14. sunshine
    January 22, 2016 at 5:43 pm

    awesome info mind blowing...

  15. Dude
    January 8, 2016 at 10:51 pm

    i pooped

    • Dude
      January 8, 2016 at 10:52 pm

      Good article - mind blown here.

  16. lman
    December 20, 2015 at 5:19 am

    you know what im going to 36 ok?done

  17. yaya
    December 16, 2015 at 7:53 pm

    i am poop.

  18. Anonymous
    October 15, 2015 at 2:21 pm

    Thanks,this page was useful

  19. Clare
    May 20, 2015 at 3:39 pm

    WOW! that is very amazing. I've heard of terabytes, but not petabytes! that is amazing to think of how vast our computer systems are, etc. This article is a massive help, thank you.

  20. roy
    March 9, 2015 at 11:35 pm

    WOW MY TROUBLE NOW IS THAT MY BRAIN HAS JUST IMPLODED hehe...... but thankyou for imformation a big help ..

  21. Faisal Ahmed
    September 13, 2012 at 1:33 pm

    "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!!!

  22. Dos Moonen
    August 24, 2012 at 5:02 pm

    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 -.-

    • Anonymous
      September 2, 2015 at 1:41 am

      Yes! I was very irked upon reading that. Get your facts straight before writing an article please. No offense, it's just bad form.

    • Mihir Patkar
      September 2, 2015 at 7:26 am

      Joel already knows this, he was trying to explain the more commonly used terms for these. While you and he might know the difference between kilo and kebi, mega and mebi, peta and pebi, and so on, common parlance does not use the binary units. No one advertises a phone as having "16GiB" and carefully explains, "That's Gibibyte, not Gigabyte. Why don't you sit down and we'll talk about binary, move on up to what the IEC is, and then hammer out details of binary prefixes vs standard unit prefixes."

      Summary: Don't be pedantic.

    • RZ
      September 13, 2016 at 11:54 am

      Mihir Patkar, "more commonly used terms" but that's just silly. it's a technical article and suppose to make it clear.. why would he use incorrect values?

  23. Evan Spangler
    August 20, 2012 at 10:07 pm

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

  24. DI
    August 20, 2012 at 2:16 pm

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

  25. josemon maliakal
    August 19, 2012 at 6:15 am

    very useful info

  26. Fayz
    August 17, 2012 at 8:46 pm

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

  27. Seishun Kyosoukyoku
    August 17, 2012 at 5:41 pm

    Thanks for Share ...

  28. Praveen pandey
    August 17, 2012 at 11:30 am

    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

    • DI
      August 20, 2012 at 2:17 pm

      nice ty!!

    • Raj
      September 5, 2012 at 6:45 am

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

    • RZ
      September 13, 2016 at 11:52 am

      why you guys ignore the fact that 10^2 is not the same as 2^10 ?

  29. Dee Wheat
    August 15, 2012 at 4:31 pm

    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!

  30. Mike Vaz
    August 15, 2012 at 3:50 pm

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

  31. Scutterman
    August 15, 2012 at 12:33 pm

    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
      August 15, 2012 at 2:46 pm

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

  32. raja
    August 15, 2012 at 8:27 am

    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
      August 15, 2012 at 2:46 pm

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

  33. Nehad Hussain
    August 15, 2012 at 8:10 am

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

    • Joel Lee
      August 15, 2012 at 2:52 pm

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

  34. Mani Ahmed
    August 15, 2012 at 4:56 am

    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 (80x286 series) i have seen 3 generations of bytes, the kilo, mega and giga, yet to enter the tera ... and now petabyte!

    thanks !

  35. Ashwin Ramesh
    August 15, 2012 at 1:44 am

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

    • Joel Lee
      August 15, 2012 at 2:46 am

      Glad it helped! :)

  36. The 24
    August 15, 2012 at 1:14 am

    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
      August 15, 2012 at 1:28 am

      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. :)

      • Scutterman
        August 15, 2012 at 12:21 pm

        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
      August 15, 2012 at 4:24 am

      I think I'll stick with political science... :)

  37. Geoff
    August 15, 2012 at 1:08 am

    The meaning of the prefixes kilo, mega, giga, tera etc. is defined by the Système international d'unités (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
      August 15, 2012 at 1:23 am

      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!

  38. Alex Shen
    August 14, 2012 at 11:50 pm

    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
      August 15, 2012 at 12:14 am

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

  39. Daniel Tanner
    August 14, 2012 at 11:16 pm

    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
      August 15, 2012 at 2:45 am

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

    • anthonymonori
      August 26, 2012 at 1:38 pm

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

  40. George. W
    August 14, 2012 at 10:38 pm

    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
      August 15, 2012 at 2:46 am

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

      • GayashanNA
        August 15, 2012 at 8:37 am

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

        • anthonymonori
          August 26, 2012 at 1:37 pm

          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!

  41. Ram
    August 14, 2012 at 10:13 pm

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

  42. Ram
    August 14, 2012 at 10:09 pm

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

    • Joel Lee
      August 15, 2012 at 2:45 am

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

    • raja
      August 15, 2012 at 8:53 am

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

    • raja
      August 15, 2012 at 8:53 am

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

  43. GrrGrrr
    August 14, 2012 at 10:06 pm

    thanks nice read.

    Hope MS windows is now able to read 4Tb drives

    • Doc
      August 14, 2012 at 10:41 pm

      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).

      • GrrGrrr
        August 15, 2012 at 9:09 pm

        how do i know if my mb has EFI?

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

        • Doc
          August 19, 2012 at 7:27 pm

          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:

  44. JohnT
    August 14, 2012 at 10:03 pm

    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
      August 15, 2012 at 2:42 am

      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

    • corbin
      February 19, 2015 at 7:20 pm


    • corbin
      February 19, 2015 at 7:26 pm

      yep get used to it go get a life and get off your computer and stop playing this "starcraft" mr.Joel Lee

    • corbin
      February 19, 2015 at 7:28 pm

      get a life u nerds

  45. Roman Vávra
    August 14, 2012 at 9:53 pm

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

    • Roman Vávra
      August 14, 2012 at 9:54 pm

      *a lot