Technology Explained

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

Ben Stegner Updated 08-05-2020

It’s easy to understand that 500 gigabytes is more than 100 gigabytes. You probably also know that a terabyte is larger than a megabyte. But if you’re not familiar with computer architecture, these are all abstract terms. While you can visualize an inch or a quart, it’s much tougher to picture a terabyte or a petabyte.


To put these into perspective, let’s look at computer storage sizes to see just how big a gigabyte, a terabyte, and larger are.

Byte Basics Explained

In case you’re not familiar, let’s first review the fundamentals of computer storage.

A bit is the smallest amount of data a computer can store. Since computers use the binary numbering system, each bit can be either a 0 or a 1. To put this in perspective, one bit is enough to store whether a value is true or false. For example, in a video game, a single bit could be 1 if the player had obtained a certain upgrade and 0 if they didn’t have it yet.

Eight bits together are called a byte, which is the building block of storage amounts. A byte can contain 256 possible values. This, for example, stores one character in the ASCII encoding standard.

Kilobytes and Megabytes

Like most measurements, as you increase in size, prefixes are used to denote larger amounts of data.


A kilobyte (KB), the first major grouping, equals 1,000 bytes. You’ll recognize the “kilo” prefix, since it’s used in other measurements of a thousand, like “kilometer” (1,000 meters). To get an idea, a text file containing about 1,000 characters equals roughly one kilobyte.

The last size before we get to larger denominations is a megabyte (MB), which is 1,000 kilobytes (or one million bytes). One megabyte holds roughly one minute of music in MP3 format. As another bit of perspective, a standard CD holds about 700MB. Keep in mind that a megabyte is different than a megabit 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 , however.

Before we move on, we should mention the difference between how computers and humans measure storage. Because of how the binary system works, one kilobyte actually equals 1,024 bytes, not an even 1,000. That variation grows as you move up the size ladder, which is much more noticeable at higher storage amounts. This is why a 250GB hard drive displays only about 232GB available.

Because the correct definition of prefixes like “giga” is an even multiple of 1,000, for simplicity we’ve used powers of 1,000 instead of 1,024 here. Other prefixes, such as “kibi” and “gibi”, correctly denote multiples of 1,024. See our full explanation on computer size formatting discrepancies Hard Drive Size Explained: Why 1TB Is Only 931GB of Actual Space Why does your PC only show 931GB when you have a 1TB drive? Here's the difference between advertised vs. actual hard drive space. Read More for more details.


How Big Is a Gigabyte?

Gigabyte memory sizes explained

You’re probably familiar with the term gigabyte (GB) since it’s the most common unit of storage for today’s devices. If you’re wondering how many bytes are in a gigabyte, remember that each level increases at a multiple of 1,000.

We’ve seen that there are 1,000 bytes in a kilobyte and 1,000 kilobytes in a megabyte. Since a gigabyte is 1,000 megabytes, one gigabyte is equal to 1 billion bytes.

In perspective, 1GB holds about 230 standard MP3 tracks. Depending on the video codecs used, approximately three minutes of 4K video at 30FPS would equal 1GB. And a standard DVD holds about 4.7GB.


Most of today’s smartphones come with somewhere between 32GB and 512GB of storage. However, computer storage drives are available in much larger sizes, which brings us to the next unit…

How Much Is a Terabyte?

Terabyte computer memory sizes explained

You can buy internal and external hard drives and SSDs available in terabyte denominations now. But how big is a terabyte in comparison?

Remember that moving to a terabyte (TB) simply ups the value by another power of 1,000. Thus, there are 1,000 gigabytes in a terabyte, and a terabyte is equal to a trillion bytes.


We mentioned earlier that a basic CD holds about 700MB and a DVD holds roughly 4.7GB. You’d thus need nearly 1,430 CDs or 213 DVDs to get one terabyte of storage!

From another angle, the US Library of Congress revealed in 2009 that its collection contained about 74TB of data. This has certainly increased over the years, but we can use other huge datasets for more recent calculations.

For example, common estimates state that the average book requires about 1MB to store (not including illustrations). In late 2019, Google announced that Google Books had scanned over 40 million titles. This means that you’d need about 40TB to store all the books on Google Books.

What Is a Petabyte?

This is the first data size that you might not be familiar with. One petabyte (PB) equals 1,000 terabytes, or one quadrillion bytes. This is a staggering amount of information that’s difficult to comprehend.

To try putting this in perspective, scientists estimate the human brain has space for about 2.5PB of memories. 1PB would be enough to store 24/7 video recording at 1080p for almost 3.5 years. You could take 4,000 digital photos every day for your entire life to fill up one petabyte, as well. And in March 2018, AT&T was transferring 197PB of data through its networks every day.

Put another way, the Milky Way Galaxy is home to approximately 200 billion stars. If every individual star was a single byte, we would need 5,000 Milky Way Galaxies to reach 1PB of data.

Exabytes, Zettabytes, and Yottabytes

Above petabytes, there are still several larger magnitudes of data storage. We’ll look at them briefly so you’re familiar with them, but these sizes are so enormous that you’re unlikely to hear them referenced in normal conversation for years to come.

An exabyte (EB) is 1,000 petabytes, or one quintillion bytes. 2004 was the first time that monthly internet traffic across the world passed 1EB. In 2017, the internet handled some 122EB of data every month. You could fit around 11 million 4K movies in an exabyte of storage.

Next up is a zettabyte (ZB), which is equivalent to 1,000 exabytes or one sextillion bytes. The International Data Corporation calculated that the global datasphere was somewhere around 33 zettabytes in 2018. As another way of looking at it, the continent of Australia is about 2.97 million square miles. If each square mile represented one terabyte, you could fit almost 337 copies of Australia into a zettabyte.

The largest currently defined data size is a yottabyte (YB). This staggering unit is equal to 1,000 zettabytes, or one septillion bytes. Comparisons with today’s data sizes are a bit ridiculous, but it’s estimated that you could fit 257.054 trillion DVDs or 288.230 quadrillion average MP3 songs in a yottabyte.

Gigabytes, Terabytes, Other Sizes: Explained!

It’s amazing to consider how far storage technology has come in just a few decades. We can now store huge collections of video, audio, images, and other data on our computers and phones that would have been unthinkable 20 years ago.

It will probably be a while before you can buy a storage drive that’s measured in petabytes or larger, but now you know roughly how much these units hold.

If you’re running out of storage, check out the best free cloud storage providers 5 Best Free Cloud Storage Providers Use cloud storage and access your files from anywhere. Let's explore the best free cloud storage solutions you can opt for today. Read More for some additional space.

Image Credit: Dooder/Shutterstock

Related topics: Computer Memory, Hard Drive, Jargon, Storage.

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  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