How to increase or decrease your Boot Camp partition

If you’re running Mac OS X and Boot Camp you may need to increase or decrease the size of your Microsoft Windows Boot Camp partition, depending on what great videos games are out for Windows at the time. 😉

To accomplish this task without losing all your Windows data you need 3 things.

  1. Mac OS X 10.5 (Leopard)
  2. An HFS+ Mac-formatted external drive
  3. Winclone

To decrease the size of your Windows partition use the following steps.

  1. Make a backup of your Boot Camp partition from Windows. (optional)
  2. Run Winclone.
  3. In the “Tools” drop down click “Shrink Windows (NTFS) file system.”
  4. Follow the onscreen instructions.
  5. Wait… it takes awhile.
  6. In Winclone create an “Image” to your Mac-formatted external hard drive.
  7. Use Boot Camp Assistant to return your drive to a 100% Mac-formatted partition.
  8. Use Boot Camp Assistant to make a new Boot Camp partition larger than the file size of your “shrunk” Windows partition image, but smaller than your original Boot Camp partition size.
  9. When it asks for Windows disk, quit Boot Camp Assistant.
  10. Run Winclone again and “Restore” your Windows image to the new partition.

To increase the size of your Windows partition use the following steps.

  1. Make a backup of your Boot Camp partition from Windows. (optional)
  2. Run Winclone.
  3. In Winclone create an “Image” to your Mac-formatted external hard drive.
  4. Use Boot Camp Assistant to return your drive to a 100% Mac-formatted partition.
  5. Use Boot Camp Assistant to make new Boot Camp partition larger than your original partition size.
  6. When it asks for Windows disk, quit Boot Camp Assistant.
  7. Run Winclone again and “Restore” your Windows image to the new partition.

Kind of a pain, but it’s doable. I’ve altered my Boot Camp partition numerous times using the methods above.

97 thoughts on “How to increase or decrease your Boot Camp partition

  1. I can’t restore. I use BC assistant to create a bigger BC partition (35GB) and when I restore it, its says the exact winclone file. Please help.

    1. The resizing only works if the windows partition is NTFS. If it is fat32, there is a way to change it to NTFS in windows.

      Open Command Prompt – Click Start, point to All Programs, point to Accessories, and then click Command Prompt.

      In the command prompt window, type: convert drive_letter: /fs:ntfs

      For example, typing convert D: /fs:ntfs would format drive D: with the ntfs format. You can convert FAT or FAT32 volumes to NTFS with this command.

      Important Once you convert a drive or partition to NTFS, you cannot simply convert it back to FAT or FAT32. You will need to reformat the drive or partition which will erase all data, including programs and personal files, on the partition.

  2. Worked like a dream! Thanks!
    After restoring the winclone image the computer ran checkdisk when I started Windows the first time. It didn’t find any errors though. It also found a new piece of hardware (???), installed a driver and had me restart again. No problems though.
    So glad this worked. Took a total of one hour maximum.

  3. WORKS!

    I have a 120 intel SSD. I originally thought I’d be on the WIN7 side of things since I bootcamped my 500gb previously. I made the switch and it looks like I can do most of everything from OSX. So I’m giving it a try. I shrunk my win7 partition, imaged it to a second harddrive, then ran bootcamp assistant to restore and repartition the SSD. Winclone restored the bootcamp partition, and I booted in WIN7, chkdsk, and shut down. Went back to OSX and my parallels profile was broken (couldn’t boot). I just had to recreate a VM using the new BC partition. All is well and now I have much more space on the OSX side.

    THANKS for the instructions!

  4. did you guys try this for win7 64bit??.. im trying to increase the bootcamp partition.. i saw a comment on winclone which had problem with restoring image.. before i start jus a double check.
    Thanks in advance

    1. @zhak: Yeah, I just tried that myself! Worked very well! Make sure you choose “BOOTCAMP” partition when restoring the image! Winclone didn’t pick that by default for some reason.

  5. I just tried this for Win7 64 Bit, and, it gets to the restore stage, then has the while/blue/white/blue line thing going along, then doesn’t go any further?
    I tried formatting the bootcamp partition to NTFS, but this hasn’t helped at all.


    1. Same problem as JYE

      Blue and white banner just scrolls and no sign of progess.

      How long should the Winclone Restore take?

      Does the image need to be mounted first?

      Does the larger partition need to be formatted with the Windows disc to NTFS before doing Winclone Restore?

      Help please!

  6. Wow it worked for me. I decreased my Bootcamp (Windows) partition and have a larger Mac partition now. WinClone is so useful!

    Took me two full hours to do the whole process, but it’s worth it than consulting with Apple Support.

  7. Why is it that when I get to step 8 in making the Bootcamp Partition bigger , that WinClone just stops to a Blue/White Ribbon in the process bar , how long does it take roughly ? Thanks for any help in advance.

  8. I’ve got just one doubt… When I’ll run “Restore to a single Mac OS partition” to return my drive to a 100% Mac-formatted partition, am I going to loose data on the MacOS partition too?

    I’d like to encrease dimension for the Win partition and I know now how to restore my Win backup, but I’d prefer not to restore also my MacOS backup…

    Thank you

  9. Hey so works fine till restoring stage when I recieved error message stating to check the log…. the log saying that cluster accounting failed. Anyone know what this is and how to fix it.


  10. If I am to do this, what do you recommend for the HFS+ Mac-formatted external drive. What does HFS mean and if I do not have one what should I get and where?

    1. HFS+ is the default partition scheme for Mac OS X. If you have a Mac that can run windows, then your drive is already HFS+ formatted.

      1. I didn’t read the entire question before. You can use disk utility to format any external hard drive as HFS+. Like I said earlier, it’s the default.

        To do so, plug said external hard drive in, open disk utility, (applications/utilities/disk utility) click on the drive in the left had menu and then click on the partition tab to the right. Under volume scheme, choose the number of partitions you want (you can go up to 16 on a single disk if you want). Make sure one of the partitions is a little bigger than the windows partition. Name the partition(s). Choose Mac OS Extended (journaled) as the format. Then click on the options button and make sure GUID is chosen. Click OK there, then click apply in the lower right hand corner of that window. Then you are set.

  11. Cory, the disk utility allows you to decrease the mac partition, but it doesn’t allow you to modify the boot camp size.

  12. Hey, Can I decrease my windows partition size without doing the ‘Tools -> Shrink Windows…’? I’ve already created the image file through Wilcone, it is 21gb. The partition is 70gb, so I want to drop it by at least 30gb.

    Also, If I do this, will I have to reinstall any programs on my windows partition?

    Thanks a lot!!

  13. Here is the error I get when I try to restore. Any Idea what I am doing wrong?

    Sat Oct 15 16:27:36 PDT 2011: Partition is : /dev/disk0s3
    Sat Oct 15 16:27:36 PDT 2011
    Sat Oct 15 16:27:36 PDT 2011: Restoring:
    Sat Oct 15 16:27:36 PDT 2011: ‘/Applications/’ -restore -copy_bcd ‘/Applications/’ -disk_device /dev/disk0 -ntfs_partition /dev/disk0s3 -v -update_bootini -q -image_dir=’/Users/gerayeremin/Documents/Bootcamp_Back.winclone’ -gptrefresh_path=’/Applications/’ -ntfstools_dir=/Library/NTFSProgs >> ~/Library/Logs/Winclone.log 2>&1 &
    getting fdisk info…..
    validating partition type…..
    checking image size…..
    image size file exists, opening…..
    reading image file…/Users/gerayeremin/Documents/Bootcamp_Back.winclone/size..
    read image file…/Users/gerayeremin/Documents/Bootcamp_Back.winclone/size..
    done calculating..
    done checking size..
    checking format of image..
    We have NTFS..
    Unmounting /dev/disk0s3
    /usr/sbin/diskutil unmount “/dev/disk0s3″return value of unmount is 0

    ==============mounting disk image==============
    /usr/bin/hdiutil attach -nomount “/Users/gerayeremin/Documents/Bootcamp_Back.winclone/Windows.dmg”

    disk device is /dev/disk1
    =====restoring image from disk image=============

    “/Library/NTFSProgs/ntfsclone” –rescue -f -f -f -O “/dev/disk0s3” /dev/disk1 1>&2
    ntfsclone v2.0.0 (libntfs 10:0:0)
    ERROR(16): Opening ‘/dev/disk1’ as NTFS failed: Resource busy
    return value of “/Library/NTFSProgs/ntfsclone” –rescue -f -f -f -O “/dev/disk0s3” /dev/disk1 1>&2 is 256

    “/Library/NTFSProgs/ntfsclone” –rescue -f -f -f -O “/dev/disk0s3” /dev/disk1 1>&2 did not complete successfully
    cleaning up: Mounting Disk
    Volume BOOTCAMP on /dev/disk0s3 mounted
    Sat Oct 15 16:27:40 PDT 2011

  14. I can’t get this to work for me either. I was able to clone the Bootcamp partition from it’s original 400GB size down to a 8GB *.winclone file. I then wiped the bootcamp partition, so the drive was entirely HFS.

    I then relaunched the Bootcamp utility on the Mac side and had it create a 150GB windows partition (which it did automatically as FAT32) and relaunched Winclone. It errored out on the restore, so I assumed that it needed the target partition to be NTFS. The only way I figured to do that was to go ahead and let bootcamp start to install Windows 7 (which errors at the start, asking to convert the target install drive to NTFS). I got all the way through the Windows install and rebooted to the Mac side.

    Tried Winclone again and again, got errors trying to restore.
    This is maddening. The log says:

    =====restoring image==============

    /usr/sbin/asr restore –noverify –puppetstrings -noprompt -erase –source “/Volumes/External PT Drive/bootcampbackup.winclone/Windows.dmg” –target “/dev/disk0s3” 1>&2
    XSTA start 156 client
    XSTA setup
    Validating target…done
    XSTA metadata
    Validating source…done
    Repartitioning target device…
    Could not change the partition type for /dev/disk0s3 – Cannot allocate memory
    XSTA fail
    return value of /usr/sbin/asr restore –noverify –puppetstrings -noprompt -erase –source “/Volumes/External PT Drive/bootcampbackup.winclone/Windows.dmg” –target “/dev/disk0s3” 1>&2 is 256

    /usr/sbin/asr restore –noverify –puppetstrings -noprompt -erase –source “/Volumes/External PT Drive/bootcampbackup.winclone/Windows.dmg” –target “/dev/disk0s3” 1>&2 did not complete successfully
    cleaning up: Mounting Disk
    Volume BOOTCAMP on /dev/disk0s3 mounted
    Thu Nov 3 17:27:52 PDT 2011

    Anybody have any clue? I’m losing hours of work here! Thanks

    1. Did you use the “Shrink Partition” option in the Winclone menu? You are going from a 400GB Bootcamp partition down to 150GB… the start of the post lists instructions on how to shrink the partition.

  15. Wow, 2.2.3 worked wonders. I’m running Lion on a new (fall 2011) Macbook Pro. I expanded a 50g partition to 100g using Winclone. The only issue was it showed up initially as Fat32. But a format button in Winclone converted it to NFTS. Thanks to the folks who updated Winclone!

  16. A tip for anyone trying to increase their BOOTCAMP partitions size:
    so far, this process seems to work (I am restoring my Winclone backup now…so far so good).
    But in step 6 under increasing partition size it says:
    “When it asks for Windows disk, quit Boot Camp Assistant.”
    That won’t work: using Boot Camp Assistant 4.0.1 (429), if you do that, the new BOOTCAMP partition will not be created. Instead, I needed to insert my Win7 64bit DVD and click OK when it was looking for the Windows install disk:
    only THEN would it create the new (larger) bootcamp partition.
    After it did that, I could see in a finder window that the new BOOTCAMP partition now showed up, and Boot Camp Assistant immediately proceeded to do other stuff (sounded like the CD was spinning up, so presumably it was about to reboot into the Windows installer): at this point I used the power button to turn off my new iMac 27″. When I booted up again (into OS X again), BOOTCAMP partition showed up fine.
    Hope this helps someone out there!

    1. strathglass is right. After reformatted my Mac HD to 100%, my BCA version 4.0.1(429) asks for the Windows installer disc to even begin the partition process. I put it in and let it run the partitioning process.

      For me, right after this process BCA becomes unresponsive and my whole Mac hung. I had to physically restart it with the button. Upon rebooting the new partition appears as it should be.

      Restoring Windows using WinClone now. Hopefully things will go smoothly from here.

  17. Strathglass, how were you able to get the win7 CD out of the machine before the bootup you wanted to take you back to OSX? On my iMac 27″, as long as the win7 remains in the drive the system boots to win7 install.

  18. I’m at the point where WinClone restores the disk image to the new bootcamp partition, which I resized from 150GB to 349, using bootcamp. However, restoring the 139GB image to the new 349GB partition has taken 4 and a half hours so far, and it’s only about 3/5th’s of the way there… is this normal? I’m not sure whether it should be taking so long or not…

  19. It’s work on my macbook pro 15″ early 2011.just follow the instruction i’ve got it to increase my Windows 7

  20. Worked perfectly for me. Thank you so much!! This article helped me resize my struggling 40gb Windows partition to a staggering 90gb Windows partition!! Not to mention I can always downsize with the instructions you left here!! You’re my hero for today man thanks again!!

  21. Boy Winclone 3.0.2 is taking extremely long to shrink my partition, it’s a 350gb partition with more than 200gb of free space, it’s been 3 hours so far. Is this normal?

  22. It appears that most everyone meets with success using this method (to increase Win partition size), but also seems that most complain that it takes a long time. I’m wondering if anyone has tried this with a solid state drive yet? Everything else is WAY faster with an SSD.

  23. Just wanted to confirm, do you only clone the windows partition to external drive or do you clone your entire drive which encompasses both windows AND mac partition?

  24. does this method keep all your installed programs? i have programs that i’ve installed, and my issue is that i want to keep them and just make the windows partition larger..

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