External 3TB Hard Drive Size Not Detected – Formatting Shows Only 349GB or 746GB

Today is the day after Thanksgiving – otherwise known as Black Friday. A friend found a good deal on a Seagate 3TB external hard drive with USB 3.0 speeds. Since he did not have a USB 3.0 port on his computer, he wanted to move his files via SATA, but when he removed it from the external enclosure and connected the hard drive straight into the computer, it only showed 349GB (or sometimes 746GB if it is a WD hard drive).

Here’s a quick explanation of what is going on and how to format the drive so that it is usable with 3TB or roughly 2.7TB due to allocation of drive space. We’ll go through the difference between MBR and GPT formats, discuss how it originally recognizes with USB and not SATA, and finally how to format the drive in Windows.


First, hard drives are typically formatted in MBR (Master Boot Record) or GPT (GUID Partition Table). When you install your operating system, like Windows XP or Windows 7, the drive needs to be formatted as MBR because that drive needs to be bootable in order to load an operating system. The MBR system will allow you to create a partition of 2TB in size, while the GPT system will allow you to go beyond the 2TB limit. So in theory, if you have an 8TB hard drive, you can only make four 2TB partitions with MBR, whereas with GPT, you can make one 8TB partition or a hundred 80GB partitions.


When you used your external hard drive, the 3TB hard drive was recognized without any problems, but when you installed it into your computer, hard drive size detection became an issue. One possible explanation is that the device is originally intended to be operated as an USB device, so the controller board is designed to get past that 2TB limit, so without the additional hardware, you didn’t see the entire 3TB as one volume.

Formatting the 3TB Hard Drive in Windows

*** NOTE: Please back up information you want to keep before formatting drive. ***
1. Go to “My Computer,” right-click on it, and select “Manage” from the menu.
2. Look for your drive at the bottom of the screen (Disk 1.. Disk 2… Disk 3.. etc..)
3. Right-click on the partition of selected drive and Delete Volume… to delete the partition.
4. The drive should show up as “unallocated partition” and may show up as two separate partitions. (One partition will be 2048GB and the other as 746GB or something like that)
5. On the left, click on the Disk # part, and click on “Convert to GPT Disk”.
6. Then proceed to format the drive as NTFS by right clicking on the partition and “Create New Simple Volume…” and go through the wizard to create a new simple volume, which will ultimately end with the options to format your drive as NTFS.
7. Open My Computer to see if you drive shows up in Explorer.
8. If it doesn’t show up, go back to Disk Management and see if the drive has been made into an active partition and also check to see if it has been assigned a drive letter. All of this can be done by right-click on the partition of the drive.

** Convert to GPT Disk is grayed out because my disk partition is not unallocated yet.**

This technique should help you utilize the maximum capacity of your 3TB hard drive. If you have any comments or suggestions, please feel free to let me know!

*Supplementary Information*
Added October 11, 2013

There are many of people who are encountering a problem where their 3TB hard drive can only format 2TB, and no other partitions are seen to be deleted or altered.  This could be due to several factors, but the following steps should help you recover the missing partition(s) beyond the 2TB, and hopefully allow your hard drive to return to its original unallocated state.

We need to wipe the drive clean and restore it.  After plugging in the hard drive, please do the following:

1. Start > right-click on Computer > go to Manage…
2. Choose Disk Management on the left hand side of the menu and check what number the drive is detected as in your list of disks.
3. The hard drive should appear in a list in the lower part of the window.
4. Remember the disk number of your hard drive.  (Disk 0, 1, 2, etc…) It’s bolded next to the partitions of the drive.
5. You can now now close this window and we will begin clearing the drive.

**All data on the hard drive will be wiped from here on.  Please back up important data.**

1.  Start > type in “cmd” in the search box below All Programs and press Enter.
2.  A black window opens up, this is your DOS command line.
3.  Type “diskpart” and press Enter to launch the Disk Partition window.
4.  Type “list disk” and press Enter to show the all the hard drives in the computer.
5.  Type “select disk #” where # is the drive disk number determined in Disk Management, and press Enter.  (i.e. “select disk 2” and pressing enter will tell the program to select the hard drive you would like to wipe clean.
6.  Type “clean” to restore the hard drive by writing zeroes for all sectors.
7.  Once finished, go back to Disk Management and check to make sure that hard drive partition is now “unallocated”.
8.  Initialize Disk if the drive isn’t initialized already, and follow the above procedures to convert the disk to a GPT disk and proceed with formatting the drive for use.

About newmeridian

Dude! When I'm right, nobody remembers, but when I'm wrong, nobody forgets...
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36 Responses to External 3TB Hard Drive Size Not Detected – Formatting Shows Only 349GB or 746GB

  1. Jokull M. Reynisson says:

    This worked out okay, except one thing… Only one unallocated partition is showing up. (The 746GB one)

    … I’d like to be able to use the other 2048GB :D
    Any help would be GREATLY appreciated.

    • newmeridian says:

      Hello… that’s an interesting problem. Since I’m not too familiar with your setup, let’s try to check this problem one by one.

      1. When you first turn on your computer and you’re in BIOS, does the computer detect that hard drive to be 3TB or only 746GB (or 785GB)?

      If so, then you can try upgrading the BIOS and possibly your Chipset driver for your current motherboard. This means if you have an Intel chipset, then I suggest trying to update your Intel Rapid Storage Technology driver. If you have an nVidia chipset, visit the AMD site. However, I’ve heard that people have had some strange problems with the nVidia drivers because it causes I/O errors, improper capacity listing, and slows down/freezes while transferring files. In that case, they have rolled back to using Window’s default drivers.

      2. If BIOS shows that it can indeed recognize the 3TB drive, then it’s not a BIOS/Hard Drive communication problem, but instead a misrepresentation between what the BIOS can support and what Windows can support. If you’re using a Windows 32-bit system, or perhaps an older version of Windows such as Win XP, that might pose a problem. But even then, you should still see at least 2.2TB of hard drive space and not only 746GB.

      3. Lastly, if it turns out that it is a controller issue where the limits of your motherboard cannot exceed that 746GB limit, then purchasing a new SATA PCI-e interface card might resolve the problem too. If this was originally an external hard drive, did it ever work via USB? If this is an internal drive, have you tried putting it into an external enclosure?

      • TValur says:

        Hi! Thanks a bunch. Helped me get from 346GB to 746GB which is an improvement but not quite 3TB or (2.7TB). My hard drive is in a dock connected to my computer via USB 3.0. It does not show up in BIOS at all. It shows up in explorer as (E:) with 746GB capacity. There was no update available for my Intel Chipset driver.

        Have you any idea what to do?

        Help appreciated!

      • newmeridian says:

        I assumed you tried following what I wrote above already, right?

        If so, please provide more info about your 3TB hard drive and your computer specs.

        We’ll go from there…

      • TValur says:

        You assumed right. :)

        http://www.seagate.com/external-hard-drives/desktop-hard-drives/backup-plus-desk/?sku=STCA3000101 I carefully removed the HD from this.

        OS Name Microsoft Windows 7 Home Premium
        Version 6.1.7601 Service Pack 1 Build 7601
        Other OS Description Not Available
        OS Manufacturer Microsoft Corporation
        System Name Valhall-PC
        System Manufacturer Acer
        System Model Aspire V3-571
        System Type x64-based PC
        Processor Intel(R) Pentium(R) CPU B960 @ 2.20GHz, 2200 Mhz, 2 Core(s), 2 Logical Processor(s)
        BIOS Version/Date Acer V1.03, 05.03.2012
        SMBIOS Version 2.7
        Windows Directory C:\Windows
        System Directory C:\Windows\system32
        Boot Device \Device\HarddiskVolume2
        Hardware Abstraction Layer Version = “6.1.7601.17514”
        User Name Valhall-PC
        Installed Physical Memory (RAM) 8,00 GB
        Total Physical Memory 7,84 GB
        Available Physical Memory 5,77 GB
        Total Virtual Memory 15,7 GB
        Available Virtual Memory 13,2 GB
        Page File Space 7,84 GB

        And those are my specs. Hope that helps you help me!

      • newmeridian says:

        Okay – so it seems that you’re trying to do this from a laptop.

        The reason it doesn’t show up in the BIOS is because many laptops are not set to boot from USB drives (HDD or Flash Drives) by default. The reason for this is to protect your system from being hi-jacked if someone comes along, grabs your machine and plugs in their flash drive. In my little explanation, I figured that people would plug that hard drive into their desktop computer via SATA because that would be the reason why people would normally want to remove the external enclosure.

        Anyway, there may be a few unknown factors here. I’m not sure how these 3TB drives respond with a third-party USB dock. Even if the USB dock supports USB 3.0, I’m not sure if your laptop does, however, it shouldn’t matter. Basically, I don’t think it’s the laptop’s fault, the dock’s fault, or the hard drive’s fault.

        The one thing you may need to do is the re-join your partitions before formatting the hard drive. So try this and let’s see if it helps any:

        1. Click on Start
        2. Right-click on Computer and select Manage from the pop up menu.
        3. On the left pane, under STORAGE, select Disk Management.
        4. You should see your drive show up. The second half of the window should show how that drive is partitioned.
        5. If it has blue tabs, then it’s formatted, if it’s black, then it’s not formatted or “unallocated”.
        6. Refer to this picture: http://h10025.www1.hp.com/ewfrf-JAVA/Doc/images/772/c01880208.gif
        7. Notice how Disk 0 has 3 partitions, two of which are blue, and the one circled is “unallocated”.
        8. The big question is… do you see your hard drive with this “unallocated” portion? If you do, please continue. If not, then stop here and explain to me what you do see.

        9. If you do see a chunk of space that’s unallocated, you will have to right-click on all of the BLUE partitions, and DELETE VOLUME…
        10. When you delete each volume, the deleted volume will join the “unallocated” space. (i.e. in the example pic above, if I had deleted the FACTORY_IMAGE (D:), the 48.83GB of unallocated space will grow an additional 11.85GB, giving me a total of about 60.7GB of “unallocated” space).
        11. Continue doing this until you just one gigantic black bar of unallocated space.
        12. Something like this: http://i.stack.imgur.com/tnQGQ.png
        13. Notice how in this image, the guy has two partitions? One of them is roughly 2TB and the other is around 700GB? The reason for this separation is because his drive has not been converted to a GPT disk and still in MBR mode. The physical limitations of MBR caps you off after 2TB, so he can’t use just one 3TB partition, unless he uses GPT.
        14. From here, just continue with what I posted in the blog, convert the disk into a GPT disk, and then format the drive.

        Let’s hope this works. If you’re stuck, let me which step you’re stuck on.

        Between Steps 8 and 9, if all you see is just one 746GB partition and no other partition, then I’m afraid that there is something weird with the USB dock connecting the hard drive via USB 3.0 to the laptop that may not be able to support 3TB. In that case, I suggest you try plugging it into a desktop PC to get the formatting and converting it into a GPT before using it on your laptop.

  2. Steven P says:

    Thankyou SO much for this! This was EXACTLY the problem I was facing! Thank you for taking the time to help others! People like you are a credit to the internet!

  3. Matt A says:

    I also appreciate the time you took to explain how to do this in a logical way without unnecessarily over complicating things. I searched elsewhere for a description on how to do this, but you’re straightforward explanation made the most sense. The problem I was experiencing was trying to partition a 3TB external hard drive that was leaving over 700GB unallocated because it was formatted as MBR. I’m glad I found your page. Thanks again!

    • newmeridian says:

      You’re very welcome! One of the hardest things to do is to communicate clearly and concisely; especially in writing. I’ve seen other forums and the information is rarely comprehensive. So it takes me forever to write an entry, but I’m glad it’s worthwhile for others. Glad you it was helpful for you!

  4. Bob Dobbs says:

    Much thanks!

  5. Kimberley says:

    I did what you said and now I am trying to format by right clicking on it and nothing in the menu says format………and it doesnt show up in my computer.

    • newmeridian says:

      Hi there – I think there may be some confusion about where to right-click. So when you click on START, move the mouse cursor over the “Computer” (if using Windows 7), and instead of clicking on “Computer”, you should right-click on “Computer” and select MANAGE. That should open up the Computer Management window then select Disk Management from the left pane, which is the first picture depicted above. Then go from there.

    • newmeridian says:

      Furthermore, it may not show up in My Computer yet due to several reasons. One, it may not be marked to be an active drive yet. Two, the drive may be unallocated, meaning that it doesn’t have a primary partition, which will require you to format the drive and create a partition. Third, if you do not see the drive present in the Disk Management pane from the Computer Management window, then please check wire connections; if connections are okay, there is a chance that may be a defective hard drive – even if the hard drive is brand new.

  6. Nick says:

    omg, u r very good. MAAAAAAANY THANKS. IT WORKS : ) !!!!!!

  7. KT says:

    Many thanks! This worked like a charm!!!

  8. andrew says:

    the step where you say right click on partition to format it to ntsf.that wasnt there when i right click on it.however create simple volume was.so i clicked on that.followed the instructions,till it took me to a window with bunch of options that included formating it to ntsf,apply drive letter etc.that worked for me.thanks a lot.

    • newmeridian says:

      Yep – you did it correctly! I was trying to summarize the steps, hoping to guide the person in the right direction instead of breaking down every step. Glad it worked out!

  9. Your method of describing everything in this article is actually pleasant,
    all be capable of easily understand it, Thanks a lot.

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  11. Mrs Syawal says:


    i using window server 2008 and i upgrade hdd wd 3tb but detect 746gb..
    hope u help my problem..

    • newmeridian says:

      Can you provide more details please? What have you tried so far? Any particular steps where you’re confused or stuck at? Keep in mind that in order to install an operating system your drive must be formatted as MBR, which will restrict you to a maximum of 2TB. I highly recommend using a smaller drive, but it’s not impossible with a 3TB drive. You just to make sure to partition it correctly.

  12. Gary Murphy says:

    That fixed it for me!

  13. Dan says:

    I purchased a 3TB hard drive and it would not recognize the drive at all. I went into Disk Management, changed to GPT, and went through Simple Volume Wizard, but the drive says the maximum is 2TB. Do you know what may be causing this? I know that my computer should work because I have used 3TB HDD’s in the past.
    I also don’t know how to bring up my computer info so if that information would help, could you please tell me how I can retrieve that information? Thanks so much!

    • newmeridian says:

      Hi – can you provide me with a little bit more info please? Is this is an external hard drive or bare internal hard drive? Make/Model if possible, or just link me to the item you purchased. Lately, I’ve seen some companies include software with the drives in order to help make this transition of formatting 3TB easier. Software has also been included with motherboards too. If it’s a product I recognize, perhaps I can point you in the right direction.

  14. Siva says:

    Hi friend I am having a similar issue but in a opposite way.
    When I am connecting my 500gb Western Digital SATA HDD through a 2.0 usb external enclosure, it is showing as 2048.00 GB unallocated under disk management console. (I am using Windows 8)
    Even I am unable to backup my files from it through various recovery tools.

    Please let me know how can I access my sata hard disk.
    Thank You in advance.

    • newmeridian says:

      Hey Siva, your situation is strange because the hard drive is showing MORE capacity than the actual capacity of the drive.

      I would like to ask a few questions to have a better understanding of what’s going on.

      1. Your WD 500GB hard drive – was this hard drive originally an internal hard drive? If so, what kind of external enclosure did you put it in?

      2. I understand you’re using Win 8. Is this from a laptop or a desktop?

      3. The WD 500GB hard drive – is it a 3.5″ one for desktop PCs or 2.5″ one for laptops?

      4. Does this 500GB hard drive have any data on it currently? If there is data on it, how was the hard drive connected before so that it worked?

      5. When you boot up the computer, does the BIOS recognize the 500GB hard drive from WD?

      Let’s hope I can troubleshoot your problem from these questions.

  15. Siva says:

    1. My hard drive is an internal one, I have received it along with my dell inspiron N5010 laptop.
    As my hard drive is of 2.5″,I am using a SSD-2501 SATA, 2.5 Sata casing (Tech-Com).

    2. I have tried to access it through my laptop and desktop, both having windows 7 & 8.

    3. It was my primary hard drive connected internally on my laptop through SATA Connector on my motherboard,

    4. I am having my data along with windows 8 OS.
    5. When I boot my laptop it didn’t recognize my WD 500 GB hard drive.Even i had tried with my desktop but no result.

    Right now I am running Stellar Phoenix Windows Data Recovery tool to check whether it recognizes my hard drive or not.

    Thank you for your assistance.

    • newmeridian says:

      So this 500GB used to be in a Dell Laptop, and you took it out, put it in a 2.5″ external enclosure, and now you’re having difficulty having it recognize the hard drive.

      The first thing I suggest is to make sure that the drive can be recognized in the BIOS. If the BIOS doesn’t recognize it, there’s a potential that the external enclosure could be at fault or the hard drive somehow malfunctioned during the move from the laptop to the external enclosures.

      Because if the computer can’t recognize the drive, then it’s hard to troubleshoot any further. Also, make sure to enable “Boot from USB Devices” in your BIOS. Sometimes, it’s disabled then you can’t see anything.

      Another thing you can do is to plug in your WD drive into the desktop machine itself. If you can access it this way, then that means that the external enclosure is defective.

      However, if it still doesn’t work, then I’m afraid that 1) the drive is somehow damaged or 2) sometimes Dell has a password lock on the hard drive so that you can’t re-use the drive on any other machine. Unfortunately, I have not been able to successfully remove the password lock on these hard drives, so I am unable to assist in that matter.

      I don’t know where you live, but if you can invest in one of these SATA to USB Adapters it will help you with troubleshooting future hard drives, http://www.amazon.com/Drive-Adapter-Converter-Optical-External/dp/B001OORMVQ/ref=pd_cp_pc_0

      Good Luck.

  16. Arsen says:

    I was tearing my hair out with this problem – only 746 gb of 3tb showing up. Tried all the various solutions to no avail until I saw your comment about the possibility of it being the hard drive enclosure. This turned out to be the case – the enclosure worked fine for drives up to 2 tb but limited the 3tb hard drive to 746 gb…… Thanks a million for your help!!!!!

  17. markd says:

    Very good advice – seems to have worked. I am just formatting my GPT 3TB external USB drive now (previously I could only get 2TB working). Diskpart is a really clever utility I never knew it was already there in Windows, up until now I have always used Norton Gdisk.

    • newmeridian says:

      Thanks – I’m glad it worked out for you! Diskpart is also good to get rid of those “locked” partitions from the manufacturer’s OS backup images on the drive itself. I think if you type in “delete partition override” or “delete volume override” or something like that, it will remove those partitions so you regain all the space on the drive.

  18. jykim315 says:

    I got it working!

    Thank you!

  19. bravejordy says:

    Thank you so much! I followed your instructions to the letter and finally got my Seagate 3TB Expansion drive up and running and showing the correct size instead of 349GB… and all in the space of a few minutes! Thank you for a crystal clear tutorial (unlike some of the ones I’ve read on other websites that leave you feeling more confused than when you started). I know it’s been said before but you, sir, truly are a credit to the Internet and to people like me who were desperate to find a simple solution to this problem without being told we need to download a whole bunch of stuff. I truly appreciate your time and effort.

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