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Maximum Size of a FAT-32 Partition

Have you ever wondered what the maximum size of a FAT-32 partition could be?

Do you have an external drive which needs to be accessed on different operating systems such as Windows and Mac OSX? Have you moved from Windows to Mac or Linux and find that you can no longer access the Windows (NTFS) drive you used for your media files? How about plugging your media library into the DVD or other player, but find that it can not read NTFS or one of the Linux formats? That means that you probably need to format your disk using FAT32.

FAT32 provides the maximum level of compatibility between OS X and Windows machines. OS X has the capability of reading and writing to FAT32 drives built into the OS, and naturally Windows can see these drives too. But what is the Maximum Size of a FAT-32 Partition?

According to Microsoft, when you use the FAT32 file system with Windows XP:

  • Clusters cannot be 64 kilobytes (KB) or larger. If clusters are 64 KB or larger, some programs (such as Setup programs) may incorrectly calculate disk space.
  • A FAT32 volume must contain a minimum of 65,527 clusters. You cannot increase the cluster size on a volume that uses the FAT32 file system so that it contains fewer than 65,527 clusters.
  • The maximum disk size is approximately 8 terabytes when you take into account the following variables: The maximum possible number of clusters on a FAT32 volume is 268,435,445, and there is a maximum of 32 KB per cluster, along with the space required for the file allocation table (FAT).
  • You cannot decrease the cluster size on a FAT32 volume so that the size of the FAT is larger than 16 megabytes (MB) minus 64 KB.
  • You cannot format a volume larger than 32 gigabytes (GB) in size using the FAT32 file system during the Windows XP installation process. Windows XP can mount and support FAT32 volumes larger than 32 GB (subject to the other limits), but you cannot create a FAT32 volume larger than 32 GB by using the Format tool during Setup.
  • You cannot create a file larger than (2^32)-1 bytes (this is one byte less than 4 GB) on a FAT32 partition.

Remember, the maximum file size on a FAT32 drive is 4GB. So if you have a file that’s larger than 4GB, you can not use FAT32. It is not uncommon for raw HD video files to be much larger than 4GB, particularly when recording live events. If you are planning to access such video files on both Windows and Mac OSX machines, do not have access to network connectivity and want to avoid third party add-ons, then download the files onto a Windows NTFS drive which a Mac will subsequently be able to access (read-only).

So according to Microsoft’s calculations above, the Maximum Size of a FAT-32 Partition is approximately 8 terabytes.

For additional information about the FAT32 file system, see the links below:

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